The chemical amplification concept is based on the use of a photochemically-generated acid as a catalyst, which indices a cascade of chemical transformations in the resist film, providing a gain mechanism. This lithographic imaging strategy invented in 1980 has been fully accepted by the microelectronics industry and implemented in manufacture of devices by deep UV lithography employing a KrF excimer laser. The resist systems currently being developed for the next generation ArF excimer laser lithography are also built on chemical amplification. This paper reviews the development, current status, and future of chemical amplification resist.

We have measured the transparencies of a number of a candidate resist materials for 157 nm, with an emphasis on determining which chemical platforms would allow resist to be used at maximum thicknesses while meeting requirements for optical density. Assuming an ideal resist optical density of 0.4, our findings show that all existing commercially available resists would need to be < 90 nm thick, whereas specialized hydrocarbon resists could be made approximately 120 nm thick, and new resists based on hydrofluorocarbons, siloxanes, and/or silsesquioxanes could be engineered to be used in thicknesses approaching 200 nm. We also assess the tradeoff between these thicknesses and what current information exists regarding defects as a function of resist thickness.

The design of 193 nm photoresists with improved reactive ion etch (RIE) resistance has been a longstanding aim of both industrial and academic research and development programs. A variety of correlations between photoresist polymer structure and etch resistance have been developed, however, the universality of these approaches, and in particular, the practicality of marking comparisons across specific polymer families and specific RIE processes has recently been called in to question. In order to examine structure: RIE correlations in more detail, we have developed a new model based on the incremental structural parameters (ISP). This model makes use of a molecular fragment-based definition of polymer structure which incorporates and extends aspects of previous parameters such as the Ohnishi and Ring parameters. An initial study revealed that this model allowed quantitative correlations between polymer families and across etch processes to be made. Continuing studies which examine the use of the ISP model in integrating 193 nm photoresists in prototype production processes will be described. Various polymer families used in deep-UV and 193 nm photoresists including methacrylates, alternating copolymers, styrenes and cyclic olefins will be compared. We will present a more detailed description of the ISP a model and of the follow-on 'new' ISP method which has been developed base don insights gained from the original ISP model, and made extended comparisons between the tow ISP models.

A series of new polymers for 193 nm single layer resist based on maleic anhydride/cycloolefin systems with minimum amount of acrylate units were synthesized. In order to minimize the acrylate content, the cycloolefin moiety of the polymers was functionalized with side groups designed to either promotes adhesion to silicon substrate and/or impart the imaging functionality. All polymers were prepared by free-radical polymerization in moderate to high yields and were characterized by variety of techniques. The initial lithographic evaluation of the new resists was carried out. It was found that acrylates can be successfully replaced with appropriately substituted cycloolefins to provide good resolution. The etch resistance of the new materials generally improves with increase in cycloolefin content. The Onishi and Kunz type plots will be discussed.

One of the major factors that seem to limit the development of practically useful 193nm resist materials has been their low reactive-ion-etch (RIE) resistance. In this paper, we have shown convincingly that the RIE stability of poly(cyclicolefins) is superior to that of the alternating copolymers such as poly(norbornene-anhydride), and poly(acrylates). We have also shown that a high performance 193nm resist can be developed from functionalized poly(norbornenes) using appropriate formulation and process optimizations.

We have investigated three substantially different routes to 193nm single layer resists. This paper will attempt to shed light on the strengths and weaknesses of each approach. Design principles, polymer synthesis and properties, and resist properties will be discussed for the three main branches of 193nm resists.

The role of block copolymers as additives for improving resist performance in the area of 193 nm lithography is investigated in this study. We have demonstrated that specifically designed block copolymers when tailored to resist matrices to which they are added can profoundly enhance resist imaging performance. This improvement can be attributed to the ability of the block copolymers to modify surface and interfaces and to control photoacid generator distribution within the resist film. Ion beam techniques such as Rutherford Backscattering and Forward Recoil Spectrometry, used to analyze the distribution and segregation behavior of the photoacid generators and block copolymer additives, will also be described.

The fundamental nature of the interaction between the polymer matrix and the cholate based dissolution inhibitors are being studied by Fourier Transform-IR (FTIR) spectroscopy. It was found that the simple cholate derivatives undergo, in a blend with poly(norbornene-alt- maleic anhydride) and in a blend with the terpolymers poly(norbornene-alt-maleic anhydride-co-t-butylacrylate) and poly(norbornene-alt-maleic anhydride-co-acrylic acid), stronger interaction as seen by shifts in the OH region of the spectra than do blends with dimeric or oligomeric cholates.

We describe a cyclopolymerization approach to novel cyclic materials incorporating a) etch-stable adamantyl esters and b) t-butyl esters as functionalities suitable for chemical amplification. The synthesis of the monomers follows a highly convergent approach from the readily synthesized 1- adamantyl malonate ester. Two polymerizable side chains are then added, incorporating either a(t-butyl acrylate esters, or b) a terminal olefin functionality. These bifunctional, carbon-rich monomers undergo smooth and efficient free radical ring-closing cyclopolymerization to afford soluble, processable polymers that do not contain residual olefinic signals. In order to optimize the lithographic performance of the materials, these crystalline monomers can also be copolymerized with maleic anhydride, or other desirable monomers. These resists show excellent transparency at 193 nm and outstanding etch resistance. When used in combination with a photoacid generator, they ca be used to formulate deep UV, chemically amplified photoresists. Preliminary imaging experiments conducted with a 193 nm ArF laser stepper exposure unit demonstrate features below 0.18 (mu) .

Carbon-13 nuclear magnetic resonance (NMR) spectroscopy has been employed in the investigation of ESCAP-related deep UV resist films. The films were first processed and then dissolved in a deuterated solvent. Quantitative data were obtained on the concentration of residual casting solvents as a function of the bake temperature and of storage conditions. In addition to accurate determination of the degree of deprotection, side reactions that occur in the resist film such as C- and O-alkylation of the phenol have been quantitatively analyzed while varying the exposure dose, bake temperature, resin structure, and acid generator. Furthermore, photochemical decomposition of several acid generator in the resist film was quantitatively monitored. This paper demonstrates that the C NMR technique can readily provide a wealth of quantitative and indispensable information about constituents and chemistries in resist films.

Norbornene-alt-Maleic Anhydride polymers have been recently introduced to fulfill the transparency and plasma durability requirements demanded for 193 nm lithography single layer resist system. Very few information exist in the literature on these new materials. This paper investigates the properties of some representative polymers of this family, and tries to draw general rules. The investigation of the physico-chemical properties requires advanced characterization techniques such as modulated temperature DSC. The copolymers of N/MA and Methacrylate monomers appear to show interesting Tg switch effect. Additional information have been obtained with the implementation of Dielectric Analysis. The high rigidity of these polymers can explain their high resolution performance reported in the literature. More generally N/MA polymers exhibit unusual properties that raise new questions on the structure of the resist film and on the process mechanisms involved.

In this paper a new method to determine photoresist DIll parameters is presented. Based on spectroscopic ellipsometry (SE) measurements, this new method is more precise than standard techniques based on transmittance measurements. Indeed, compared to photometry, SE technique is a self calibrated technique which provide directly two independent parameters Tan (Psi) and Cos (Delta) which can be used to extract directly thickness but also optical indices of a layer inside a multilayer structure. Moreover, the wavelength dependence introduces more restrictions for the data analysis since thickness and optical indices can be deduced directly in many cases. We apply this technique to different kinds of photoresist designed for 365nm and 248nm. At each wavelength ellipsometric parameters are simulate directly versus the exposure dose without any assumption on the thickness and on the index of refraction evolution. On 365nm photoresist this new method provides Dill parameters in good agreement with the standard method. On 248nm photoresist we show that the influence of the exposure is more important on the refractive index and on the thickness of the layer than on its absorption.

The detailed structure of the 3D relief image formed upon processing a chemically amplified (CA) resist film is the result of a complex interplay of the projected optical image, the resist optical and photochemical properties, and the chemistry and physics of post-exposure thermal processing. During post-expose heating,the initial latent image of photogenerated acid is transformed into a developable chemical latent image of deprotected polymer whose form is governed by the kinetics of both a thermally- activated chemical deprotection reaction and the diffusion of photo-generated acid within the polymer film. WHile there have been recent advances in characterizing the chemistry and kinetics of deprotection in CA resist films, at present our fundamental quantitative understanding of photo-acid diffusion remains poor.

We have investigated the effect of line edge roughness (LER) of active patterns used for shallow trench isolation to the electrical performance of MOS transistor applicable for 1 giga-bit DRAM. Three different processes for resist patterning were applied for comparative analysis to form the active pattern in MOS transistor; the first method applied a conventional single layer resist (SLR) process, the second TIPS with two step dry development, and the third another TIPS with three step dry development. The third process adopted an additional step to break-through thin silicon dioxide which may contribute to the LER. The LER data of an active pattern before and after nitride substrate etching and their profiles were investigated among these processes. The third method shows the almost same LER and CD uniformity of the active pattern as those of SLR. The electrical properties. Only, threshold voltage variation of MOS transistor by the second method shows the worse results than those of SLR. Considering the ratio of LER in isolated active pattern with channel width of 0.3 micrometers to its average CD value, we think that its ratio should be controlled well below 7 percent for TIPS to make an useful technology for real device. Based on these studies, we believed that the well-controlled TIPS process using three step dry development is a strong candidate for device production of ArF and EUV lithography, if the advantages of TIPS technology over the SLR process are considered in the respect of lithography.

Interferometric lithography affords the unique ability to independently control dose, pitch and aerial image contrast during photolithographic exposure. In this report, we describe the use of a deep-UV interferometric lithography exposure tool to study the impact of aerial image contrast on resists imaging properties. A wide range of high resolution resists materials was surveyed, including positive- and negative-tone systems, chemically amplified and conventional diazonaphthoquinone imagining chemistries, and aqueous- and solvent-developed systems. In all cases, resist line- edge roughness was observed to increase as aerial image contrast was decreased, though the precise behavior varied with resist material. Polymer molecular weight was systematically varied with resists materia. Polymer molecular weight was systematically varied in a negative- tone chemically amplified resist formulation. The results indicate that molecular weight is a significant factor influencing the magnitude and type of line-edge roughness at low aerial image contrast.

Methacrylates were the first class of resist to be examined for use in 193nm lithography. They are still useful today, but have a very different molecular structure because of the requirements for development in 0.262N tetramethyl ammonium hydroxide and high etching resistance. A major driving force for their continued use is the availability of a wide variety of methacrylate monomers and the use of free racial polymerization which imparts a wide range of properties to the polymers and makes them very cost effective.

Inorganic SiON BARC has been used widely in I-line lithography and 248nm DUV lithography because of its good photo performance and tunable reflective index (n) and extinction coefficient (k) on specific substrates. Conventional single layer SiON BARC on poly, WSix or Al (TiN) has successfully enhanced CD control. However, when applying single layer SiON BARC on top of oxide hard mask, tight thickness control of hard mask becomes a major issue in order to maintain the substrate reflectivity for good photo performance. Dual layer SiON BARC presented in this paper resolves the issue with wide range of hard mask thickness control. Unlike conventional organic BARC where the absorption is the primary mechanisms and the conventional single layer inorganic BARC where phase shift cancellation is dominant, the dual layer BARC uses both phase shift cancellation and light absorption mechanism. The design of dual layer BARC is that top layer serves as phase shift cancellation layer and bottom layer serves as light absorption layer with high k value. Therefore, with fixed bottom absorption layer, top layer n and k and thickness can be fine tuned to get the best photo performances. The advantages of dual layer SiON BARC are that there is no need for the tight BARC thickness control as in the case of single layer SiON BARC as well as for hard mask thickness control. Since the light is all absorbed by the bottom BARC layer, the periodical phenomena of light passing through transparent hard mask film does not exist. Detail information of setting up dual layer SiON BARC by both simulation and experiment are described here. The comparison between dual layer BARC and single layer BARC shows that smaller swing ratio and tighter CD control can be obtained in the case of dual layer BARC. Similarly, the comparison between dual layer SiON BARC and organic BARC shows that smaller iso-dense bias and better resist profile can be obtained with dual layer SiON BARC.

The interaction between a chemical amplification (CA) resist and a bottom anti-reflective layer (BARL) was clarified to find ways to suppress the resist pattern deformation in the BARL. A SiON film, which is a candidate for use as a BARL material, was analyzed by Fourier transform IR attenuated total reflection spectroscopy, thermal desorption spectroscopy, and x-ray photoelectron spectroscopy (XPS). The Si-NH_x, Si-NSi₂, Si-OH and Si-OSi groups were identified as the interaction sites on SiON. The effects of those sites on the acid that catalyzes the in-resist reactions were estimated with the partial charge and the at of formation calculated by a molecular-orbital method. The calculation results indicated that the Si-NH_x groups completely decompose the acid, and the Si-OH groups decompose it to some extent. The other groups only trap the acid. The strong acid has high affinity and reactivity with those sites. However, a strong acid making a weak bond with the sites on SiON is likely to have a high catalytic ability. This advantage of the strong acid was confirmed by pattern delineation with a resist including onium-salt- generating CF₃SO₃H.

Application of polysilanes for a deep UV (DUV) bottom anti- reflective coating (BARC), in order to resolve the problem posed by the insufficient anti-reflection with thin conventional organic BARC applied on transparent dielectric film, is described. The newly developed polysilane anti- reflective coating has the real part of refractive index, n equals 2.00, and the imaginary part, k equals 0.23 at 248 nm. The polysilane coating is immiscible with a chemically amplified photoresist, and is not removable during normal wet development of photoresist. Etching rate of the polysilane is 2 times faster than that of DUV resist during BARC etching, and lower than that of DUV resist during dielectric film etching. The polysilane layer is easily removed by ashing using O2 gas process. Using thick polysilane coating, it can realize both the suppression of the interface reflection between the resist and BARC and good critical dimension control on dielectric film.

Two families of polymers have been prepared and evaluated as silicon-containing bilayer resist candidates at both 193 nm and 13.4 nm (EUV). Both families of polymers are based on a tertiary ester protecting group in which the ester group contains a silicon cluster. The PRB family of polymers are random methacrylate copolymers and the PRC family are alternating maleic anhydride/norbornene polymers. The PRB family shows good resolution and sensitivity at both 193 nm and EUV, but suffers from adhesion failure between the imaging layer and the underlayer. The PRC polymers show good adhesion to underlayers and can print features at <EQ 0.12 micrometers at 193 nm and <EQ 0.10 micrometers at 13.4 nm.

Through a series of statistical design experiments we optimized the lithographic performance of a 193 nm single layer resists based on a norbornene-maleic anhydride matrix resin. Several interesting findings were found including that having the PEB temperature improved the performance of the resist. The polymer composition was found to strongly influence the lithographic performance of the resist. Variables that we examined included acrylate loading and blocking level. By optimizing the composition of the polymer, we have obtained resist with high etch resistance, square profiles and 0.130 micron dense line ultimate resolution in 0.5 micron thick films. The resist formulations are compatible with industry standard 0.262 N TMAH. During exposure the resists does not suffer from the outgassing of volatile species.

We have newly developed a novel multi-functional monomer. Application of this monomer also allows us to introduce another unit to further improve its etch resistance. Furthermore, our novel resist containing this multi- functional monomer exhibits an excellent adhesion to Si substrate, an improved CD linearity, a high sensitivity, a good contrast, and a high synthetic yield. A 110nm L/S pattern was successfully at 1:2 pitch of a strong PSM was also successfully obtained by using a 2.38wt percent TMAH aqueous solution as a developer.

Bilayer thin film imaging is one approach to extend 248 nm optical lithography to 150 nm regime and beyond. In this paper, we report our progress in the development of a positive-tone bilayer resist system consisting of a thin silicon containing imaging layer over a recently developed crosslinked polymeric underlayer. The chemically amplified imaging layer resist is based on a novel dual-functional silicon containing monomer, tris(trimethylsilyl)silylethyl methacrylate, which in addition to providing etch resistance, also functions as the acid sensitive functionality. The stabilization of (beta) -silyl carboncation by silicon allows this moiety to serve as an acid sensitive protecting group. Thus high silicon content and high resist contrast are achieved simultaneously. Lithographic evaluation of the bilayer resist with a 0.63 NA and a 0.68 NA 248 nm exposure tool has demonstrated resolution down to 125 nm equal line/space features with a dose latitude of 16 percent and depth of focus (DOF) of 0.6 um. The dose latitude and DOF for 150 nm equal line/space features are 22 percent and 1.2 um, respectively. Finally, residue-free, ultra-high aspect ratio resist features have been obtained by O₂ or O₂/SO₂ reactive ion etching using a high-density plasma etch system. The resist design, deprotection chemistry, lithographic and etch characteristics of the top layer, as well as the design of the new underlay, will be discussed.

Top surface imaging (TSI) techniques have been studied in order to enlarge the process window for fine pattern fabrication. We have been evaluating the silylation process for 193 nm lithography as one of the TSI techniques, and in this paper, we would like to focus on the effect of the silylation resist thickness of the process window. We found that a very thin silylation resists was effective in widening the fine pattern fabricating margin, and we tried to use a thin silylation resist as the top layer of the bi- layer resist system for practical applications. In order to fully realize the ability of this bi-layer silylation process, we optimized the dry-development conditions and resist structures before evaluation of the lithographic performance. A negative tone resist was used in our bi-layer silylation process, and positive tone patterns were generated after the dry-development. In this process, the depth of the silylated area was controlled, and the excess swelling caused by too many silylation reactions was restricted. Moreover, the profile of the silylated area was formed into an almost rectangular shape which was good and appropriate for precise critical dimension control. The process window was significantly enlarged, and the 0.11 micrometers L/S patterns were successfully fabricated without using any resolution enhancement techniques. We confirmed that the bi-layer silylation process is one of the best approaches to improve the lithographic performance of the silylation process.

The effect of different photoadditives in high and low activation energy resist resins on resist outgassing during lithographic exposure was studied by quartz microbalance and gas chromatography/mass spectroscopy techniques. The resist outgassing was analyzed both qualitatively and quantitatively and structure-property relationships were developed between resist outgassing and the molecular structure of photoacid generators and additives. The photoadditives examined include, aryl iodonium perfluoroalkylsulfonates, triarylsulfonium perfluoroakylsulfonates, photogenerators of sulfamic acids, 2-nitrobenzyl PAG's and doxyl derivatives.

High activation energy, chemically amplified resist systems exhibit a 4 percent to 15 percent volume shrinkage during the post-=exposure bake process. Current lithography process simulators do not take this volume shrinkage into account, thus violating the continuity equations used to model the process. This work aims at describing the kinetics of the post-exposure bake process by tracking the volume shrinkage observed in high activation resists. A dynamic model is derived and corroborated with experimental results for Shipley UV5. A global simulation technique is then used in conjunction with the models to extract the lithography parameters for these resists.

Synthesis of new alicyclic (meth)acrylate polymers containing androstane moieties, especially cholic acid derivatives, and their characteristics were investigated for 193nm single layer resists. Among the derivatives, a work of adhesion, Ohnishi and ring parameters were used as measures for the adhesion and the dry-etching resistance in this study. In the synthesis of the polymers, the use of 3- (beta) -methacryloyoxy-deoxycholic acid, which is the inverse configuration against the original 3-(alpha) -structure, was effective as a monomer, because the steric hindrance at 3- (alpha) -position degraded its polymerization ability. The polymers partially protected by acid labile groups showed a satisfactory adhesion, which was probably due to the hydrophilic hydroxyl group at the 12-position and the carboxyl group linked at the 17-position, and a good dry- etching resistance. On the lithographic imaging with these polymers, the reduction of the side reaction on the acid decomposition and also the control of the flexibility on the polymers largely affected their performance. THe adjustment of the Tg values of the polymers by the co-polymerization and the change of the polymer backbone from the methacrylate to acrylate structure performed well on imaging under 193nm exposure.

We describe the fabrication of the world's smallest fully functional conventional non-volatile memory device using 193 nm lithography for all levels. The cell area of the smallest devices fabricated was 0.0896 micrometers ². The critical level of the device, to define the channel length, was exposed with an alternating aperture phase shift mask. Floating gate dimensions ranged from 0.080 to 0.14 micrometers . Subsequent lithography, to define the control gate utilized a binary mask with gate dimensions down to 0.16 micrometers . A multi-layer ARC was used to reduce substrate reflections and maintain linewidth control over topography. All levels were exposed with a new single layer chemically amplified resist developed for 193 nm lithography. We will present results for line width control, etch bias, implementation of resolution enhancement techniques as well as issues with process integration.

This paper describes the effects of the blocking level of polymer on both dissolution characteristics and lithographic performance in chemically amplified positive 193 nm resists consisting of a alicyclic methacrylate polymer and a photoacid generator. There were clear relationships between the blocking level and both the dissolution rate characteristics and the lithographic performance. We found that the dissolution contracts and developer selectivity improved as the blocking level of polymer increased, and then the resolution capability was improved. However, the dry-etch resistance and adhesion property of the resist film deteriorated as the blocking level increased, although these were at the same levels as those of conventional i-line novolak resist or polyhydroxystyrene base KrF resists. Therefore, these resist materials show potential for the next generation of LSI devices. Ideal dissolution parameters for improving the resolution capability were obtained by using a resist profile simulator. By using a high-contrast resist incorporating these parameters, and by using a higher numerical aperture lens and annular illumination, the mass production of next-generation devices with a 0.12 micrometers design rule can be achieved.

The fundamental basis of resist performance in semiconductor lithography is the creation of a dissolution gradient in the resist film. For positive resists the dissolution rate (DR) and dissolution characteristics of the exposed as well as unexposed regions are important factors in determining the performance of the resist. Since the establishment of the dissolution rate curve as a method for evaluating photographic materials, many investigators have tried to correlate dissolution rate data with lithographic performance in a systematic way.

Plasma polymerized organosilane resists films have been shown to exhibit high sensitivity to DUV radiation. We have previously demonstrated a 193nm CVD photoresist process in which plasma polymerized methylsilane (PPMS) is patterned via photo-oxidation, dry-developed, converted into silicon dioxide, and then transferred into an underlying Si layer with high selectivity. The PPMS resist exhibits linearity down to a resolution of 130 nm L/S for a 1:1 pitch. We have demonstrated 100 nm Iso-lines at 28 mJ/cm² dose with 11 percent dose latitude and 600 nm focus latitude. Depths of focus greater than 500 nm have been demonstrated for 160 nm nested L/S.

In recent years, photoresists suppliers have migrated to offering a full palette of resist chemistries and processes which are specifically tailored for particular pattern types and/or exposure processes. Thus we now see designations such as 'contact resists', 'isolated line resists', 'dense line resists', 'attenuated phase shift resist', etc. This specialization offers the lithographer more choices for continual performance improvement and optimization, but implementation of multiple resist platforms in manufacturing can be problematic. In this paper, we examine the design criteria and efficacy of pattern- and application-specific photoresist versus a generic 'multi-purpose' material, and identify some of the trade-offs which can be expected when employing these resists. Generalized ideal resist behaviors are presented for different pattern criteria, including proximity bias. Both experimental and simulation results are given.

Lithographic scaling entails continuously increasing resolution while at the same time improving the tolerance control on the printed images. Typically, this has been done by using shorter actinic wavelengths, increasing numerical aperture, compensating reticle patterns and similar methods that serve to enhance the fidelity of the aerial image. In some case, this scaling has been achieved by altering the method of image formation, such as with the use of alternating phase shift reticles, in which the width of the aerial image is established by phase interference rather than of a diffraction-limited process of passing light through a dark masking pattern. This paper describes development of a resist material that provides a new way to scale lithographic patterns, one similar to alternating phase shift lithography in the sense that it prints the edge of an aerial image rather than the entire image as a single pattern. Because the edge of the aerial image is of higher resolution, with smaller components of tolerance than the entire image, this type of resist may provide a new method of scaling.

Polyphotolysis is an important aspect of Novolak- Diazonaphthoquinone resist. It makes for higher lithographic contrast and leads to higher line resolution. We have found that the effect depends on the interaction between phenolic strings emanating from the acceptor groups of PACs meet and connect with each other at quadrupolar nodes. After partial exposure some of the strings are severed from their anchors, but at this point they may be reconnected to still polarized, 'living' strings. In scavenging the severed, 'dead' strings the still 'living' strings increase in length so that, on exposure, two shorter polarized strings are now replaced by a singe longer polarized string. Since inhibition depends on the number of phenolic units taking part in polarized strings, partial exposure of the resist film does not much change the dissolution rate, and only the last stages of exposure produce the dramatic change in dissolution that is reflected in a steep exposure curve and in the higher image contrast of the system.

The diffusion process of acids plays important roles in chemically amplified resists. Polymer matrices from the diffusion path, and the structure significantly influences the behavior of the acid diffusion. We have simulated the diffusions of molecules in polymer matrices by molecular dynamics in order to analyze the diffusion mechanism in chemically amplified resist syste. To represent bulk state conditions of the polymer film, we prepared the molecular structures under the 3D periodic boundary conditions utilizing the molecular simulation. This amorphous cell contained three chains of methacrylate polymers such as poly(methacrylate), poly(tert-butylmethacrylate), poly(isobornylmethacrylate) and one diffusion molecule such as oxygen and methanesulfonic acid. The structure was energy-minimized and equilibrated under stable conditions. The free volumes in the system were estimated as the volumes enclosed by the iso-potential surfaces around the polymer using the Gusev-Suter method. The average size of the free volumes in the poly(methylmethacrylate) system was obtained as 3.7 angstrom³ with large standard deviation of 11.1 angstrom³, which indicates the large width of the size- distribution of free volumes scattered at random in the system. Molecular diffusion in the energy-minimized cell was simulated for 50 picoseconds by the molecular dynamics. The time dependence of the mean-square displacements of diffusing molecules was obtained from the dynamics treatments and it determined the diffusion constant in the resist systems. It is shown that the molecules do not always rapidly diffuse with larger free volumes, but the diffusions also depend upon the interaction with the polymer, and that the computer simulation tools provide the potentia for the molecular level study of resists chemistry.

Inorganic or organic bottom antireflective layers (BARL) are extensively integrated into state-of-the-art KrF excimer laser based DUV lithography processes as an effective means to suppress thin film interference effects and to enhance the yield of critical devices produced by the most advanced manufacturing lines. These improvements result primarily from better critical dimension (CD) control on reflective and topographic substrates. The use of organic polymer based bottom antireflective coatings (BARC) offers significant cost of ownership and logistic advantages, which are, however, sometimes traded off by increased particle formation during processing, which requires sophisticated inspection controls or may even give rise to an electrical nonperformance of the devices. For a reduction of the particles both, an optimization of the BARC/photoresist combination, as well as an understanding of the failure mechanism are essential. In this paper, we report about the formation of residues in a specific BARC/photoresist combination observed in the exposed areas after the dry etching process. It was found out that the chemical nature of the photoacid generators (PAG) employed in the chemically amplified photoresist (CAR) has a pronounced influence on the degree of micro particle formation and it is assumed that a photochemical interaction between the PAG and the organic polymer based BARC generates these etch resistant micro residues. More detailed studies have revealed that aromatic onium type PAGs containing photoresists tend to form higher concentrations of residues compared with otherwise identical photoresists employing non-ionic sulfonic acid producing PAGs.

Lithographic properties of a variety of acetal-derivatized styrene based polymers are reported. The structural modifications in the polymers involve varying the size of the pendent acetal moiety. the lithographic performances of the resists containing structurally modified acetals were found to be superior to the conventional acetals. In the cases where the acidolysis products of the modified acetals are non-volatile alcohols, the post-exposure volatilization, film shrinkage and plasma etch resistance were found to be significantly improved.

We have examined alicyclic polymers with a (gamma) -hydroxy acid structure in order to investigate the properties of (gamma) -hydroxy acid and (gamma) -lactone as function groups of ArF negative resist materials. From the viewpoint of transparency and dry-etching resistance, (gamma) -hydroxy acid and (gamma) -lactone structure were found to be suitable for ArF negative resists materials. Surprisingly, the reactivity of the acid-catalyzed reaction of (gamma) -hydroxy acid is affected by the polymer structure. Using ArF excimer laser stepper, 0.20-micrometers line-and-space patterns without micro-swelling distortion were obtained from a negative resist consisting of alicyclic polymer with the (gamma) - hydroxy acid structure and a photoacid generator. Distortion was avoided because the number of carboxyl groups decreased drastically in the exposed area by the acid-catalyzed intramolecular esterification of (gamma) -hydroxy acid to (gamma) -lactone. As a result, (gamma) -hydroxy acid and (gamma) -lactone structure were found to be suitable function groups for ArF negative resist materials.

Poly(2-trimethylsilyl-2-propyl methacrylate-co-(gamma) - butyrolactone-2-yl methacrylate) was synthesized and evaluated as a potential dry-developable chemically amplified photoresist. When the counterion of the photogenerated acid does not provide a fluoride ion, e.g., sulfonate, the carbonium ion undergoes elimination to produce 2,2,3-trimethyl-2-silabut-3-ene, and regenerates another acid. The deprotection of 2-trimethylsilyl-2-propyl group of the polymer takes place in the exposed region after post-exposure bake. The difference of silicon content between the unexposed and exposed regions is large enough to form patterns using oxygen reactive-ion etching. Poly(2- trimethylsilyl-2-propyl methacrylate-co-(gamma) - butyrolactone-2-yl methacrylate) was evaluated as a resists for ArF excimer laser lithography. 0.24 micrometers line/space patterns were obtained using the conventional developer with an ArF excimer laser stepper. 1 micrometers line/spacer patterns were obtained using dry development process with O₂ reactive ion etching.

The modification of the i-line resist structure after spiking with various amount of poly(4-vinylphenol) polymer is characterized by the spectra of UV visible and gel permeation chromatography. The chemical structure of photoactive compound is found to be unchanged after modification, while slight change in the polymer chain is observed. The resist layer coated onto the wafer is characterized by various methods including n and k analyzer, Nanospec, Fourier transform IR red, thermogravimetric analysis, and differential scanning calorimetry to fully evaluate the film properties in terms of porosity, thickness, vibrational spectrum, and thermal stability. Our thermal analysis results show that the resists are mainly decomposed in three stages. The photoactive compound is found to decompose during the first stage, while the polymer decomposes during the latter stages. The resist exposure parameters, namely, A, B and C at 365 nm are determined by the absorbance measurement. The extracted parameters are further used in the resist profile simulation by PROLITH/2. It is shown that the spiking of poly(4-vinylphenol) polymer into the resist can improve the resolution and linearity for dense lines. In addition, the swing effects can be reduced by up to 35 and 31 percent for dense and isolated lines after resist modification, respectively.

On the basis of the synthesis of novolac, resol resins and phenolic resins with carboxyl groups, several interesting results are found from the analyses on their properties and microstructures. It is indicated that the reactivity of some carbon atom on the benzene ring of a phenolic compound can be determined by its calculation of quantum chemistry or its C-NMR spectrum in its addition reaction and condensation polymerization with aldehydes, or in its addition reaction and polymerization with conjugated polyene compounds. In general, the lower the net charge values of some carbon atoms on the benzene ring of a phenolic compound, the lower the chemical shift values of the carbon atoms in its C-NMR spectrum, the greater the reactivity of the carbon atoms. The reactivity of a phenolic compound with a carboxyl group in its decarboxylation reaction can be determined in the same way. These conclusions are very important for the molecular design and the control of synthesis conditions of novolac, resol resins with carboxyl group. It is also of great importance for the design of resists and thermo- sensitive compositions used for thermo-sensitive CTP plates.

Currently, TMAH 2.38 percent concentration developer is popular to run photo process form g-line, I-line to DUV. For next generation photo process, the PR thickness will be thinner, CD and PR profile control are more important, so developer process will be more critical. The influence of developer concentration on DUV process performance has been investigated in this paper. We have tested 5 samples of TMAH concentration developer from 1.6 percent to 2.38 percent with one kind of DUV photoresist. The data of 0.25 micrometers L/S and 0.3 micrometers hole of masking linearity, resolution, total exposure latitude, focus latitude, and resists profile have been collected and analyzed. The optimal concentration of developer is described. Besides, 10 DUV photoresist with optimal concentration developer are tested and compared with general developer. Some chemical structures of DUV photoresist are also discussed in this paper.

We have developed a three-component negative resist for x- ray lithography which is composed of monodispersed polyhydroxystyrene as a base polymer, hexamethoxymethylmelamine as a cross-linker, and alicyclic- bromides containing ketonic groups as an acid generator. To enlarge the contrast of the dissolution rate between the exposed and unexposed films, polyhydroxystyrene was partially protected by t-butoxycarbonyl groups and organic bases were added to the resist component. Among the bromic compounds we evaluated as acid generators, the alicyclic- bromides containing ketonic groups produced hydrobromic acids most efficiently. The resolution of the new resist remains nice down to 80-nm line-and-space patterns at a proximity gap of 20 micrometers , and 70-nm patterns at a gap of 10 micrometers with a resist sensitivity of 150 mJ/cm².

In this work, a new resist silylation simulator called STIL has been developed. This simulator models the silylation process as a 1D Initial Boundary Value problem which is then solved using in-house developed Finite Element Analysis code. In this model, the silylating agent diffusion and reaction rates are recalculate dafter each silylating time- step, (delta) t. The swelling mechanism is modeled as a Boundary Movement problem whereby the swelling in each element is a function of the local silicon concentration in that element. By solution of this system across the exposed area, a 2D profile of the silicon concentration is determined over an exposed linewidth. the simulations from this model are compared to published experimental data.

The number of lithographic applications that require the use of photoresist thickness of one hundred microns or more is rapidly increasing. Extremely large structure heights and high aspect ratios are often required for micro- electrodeposition of mechanical components such as coils, cantilevers and valves. These ultra-thick photoresist can also be used as a mold in micro-electromechanical systems. Ultra-thick photoresist are also used in bump bond applications to define the size and location of the bonds for advanced flipchip packaging.

A kind of naphthoquinone diazide esters which has strong surface inhibition on exposed area has been found and is applied to non bulk effect and higher resolution i-line photoresist fabrication. Overall developing time, it consists of dissolution time of the surface inhibition layer and developing time of exposed photoresist under the surface inhibition layer and to control the dissolution time and the developing time results in non bulk effect photoresist fabrication, and where DRM, Development Rate Monitor, was used to analyze this phenomenon.

We reported the novel alkali decomposable additives improve dissolution contrast in quinonediazide type positive resists. We have found that NHSE also improves dissolution contrast in chemically amplified negative resists. Good profiles and resolution are obtained by adding NHSE in the chemically amplified negative i-line resist system.

We compared 2MAdMA(2-Metyl-2- Adamantylmethacrylate)/GBLMA((gamma) -butyrolactone methacrylate) resin system and 2EAdMA(2-Etyl-2- Adamantylmethacrylate)/GBLMA resin system. 2EAdMA/GBLMA resin system showed higher sensitivity, dissolution contrast and better adhesion to silicon substrate than 2MAdMA/GBLMA resin system. These results shows that 2EAdMA/GBLMA resin system is suitable for practical ArF positive resist.

A study for a new organic bottom antireflective coating (BARC) composition is described. A structural design of a light-absorbing dye was most important because dye structure not only plays a role in eliminating reflection from a substrate but also shows influence on dry etch rate of BARC material to a considerable extent. For example, an anthracene moiety with large absorption at 248 nm had undesirable dry etch resistance. 3-Hydroxy-2-naphthoic acid moiety was found to be one of suitable dyes for KrF BARC compositions, and the polymer bearing the dye showed enough absorbance and good erodability in dry etch. The BARC polymer was eroded as one and a half times faster than a novolak resin, and a little faster than an anthracene incorporated polymer. The result was discussed from the concepts of Ohnishi parameter and the ring parameter for dry etch durability of resist materials. BARC polymer should be thermoset by hard bake to eliminate intermixing with resist compositions. The BARC polymer bearing hydroxy group which is useful for a crosslinking reaction was thermoset in the presence of melamine-formaldehyde crosslinker and an acid catalyst after baking over 200 degrees C.

Structurally modified acetal resist is designed for lithography on metal layers. The acetal-based polymer used in the resist has intrinsically low post-exposure volatilization and superior metal etch resistance. This resist is designed to have excellent substrate compatibility as indicated by a foot size of less than 10 nm for 250 nm feature size. Lithographic evaluations reveal that this resists is capable of resolving sub-200 nm features on TiN substrates with high photosensitivity, dose latitude and excellent process windows for line and post features. The reduced foot size and enhanced resolution could be achieved by optimizing the resist chemistry and the processing conditions.

A chemically amplified resist containing a basic monomer, 3- (t-butoxycarbonyl)-1-vinylcaprolactam (BCVC), in the matrix polymer was synthesized with various monomer feed ratios. Diffusion and evaporation of photogenerated acid in the copolymer films were investigate for various fractions of the basic units in copolymers. It is found that only acid surviving deactivation by the BCVC units diffuses into unexposed areas and evaporates for the copolymer film to bleach the indicator film. Evaporation of a low molecular weight basic additive is also examined. Whereas the low molecular weight basic additive evaporated during baking, the basic monomer units in the copolymer did not evaporate at all due to covalent bonding to polymer backbone chain. Thus, the copolymer with the basic monomer can control the acid diffusion and evaporation effectively. The new resists system enables us to form fine patterns even after post- exposure delay of 2 h without any additional treatment.

Scanning probe lithography (SPL) has recently been shown to be a versatile technique for patterning semiconductor surfaces. The intense electric field emanating from the scanning probe tip can be used for the patterning of carbon- based self-assembled monolayers and thin films, as well as the anodization or field-enhanced oxidation of passivated metal surfaces. We have been investigating the use of monolayers and ultra-thin films made from dendritic polymers as resists for SPL. Dendrimer films have ben prepare by both covalent and ionic binding to the wafer surface. Silicon wafers were treated with dendritic chlorosilanes to afford self-assembled monolayer from the functionalized dendrons. Ionically bound dendrimer films were prepared by treating an aminopropylsilane-modified wafer surface with a dendritic carboxylic acid. These ultra-thin dendrimer films were characterized by atomic force microscopy, contact angle goniometry, and optical ellipsometry. The dendrimer films were shown to be effective resist for SPL, and we have patterned negative tone oxide images onto dendrimer modified wafer surfaces. Pattern transfer can be achieved by a selective wet etch resulting in the formation of positive tone images.

The present paper discusses theory, design and properties of bottom anti-reflective coatings (BARCs) for deep UV and i- line applications. All BARCs are interference devices, and as such their optical constants are optimal only for certain combinations of thickness and the real and imaginary parts of the refractive index. Maps of the optimality conditions in the parameter space will be provided. The design of BARCs for various exposure wavelengths involves choosing the right dye molecules capable of highly absorbing at the particular wavelengths and optimizing the etch rates of the resulting film sand fine tuning the formations for best lithographic performance. At an exposure wavelength of 365 nm, dye compounds such as amino aromatic or azo type compounds can be used, for 248 nm it is necessary to use fused rings such as anthracene to have sufficient absorption, and in the case of 193 nm exposures simple benzene or phenolic compounds exhibit the required d absorbance. Since the dye molecules are invariably aromatic or fused rings, it is necessary to balance the absorption property versus the etch rate by incorporating non-aromatic moieties. Further, the BARC formulations need to be free from intermixing, formation of foot or undercut in order to obtain fine resist patterns. Our development efforts on BARCs have led to the AZ EXP ArF, KrF and BARLi series of BARCs designed for 193, 248 and 365 nm wavelength exposures, respectively. Lithographic data of some of these products will also be presented with the emphasis on the AZ EXP ArF-1 material designed for 193 nm exposure.

We have prepare several novel silicon-containing polymers containing both low E_a and high E_a protecting groups, and we have evaluated these materials at both 193 nm. Low E_a acetal-containing polymers were prepared by reacting poly(4-vinylphenol) with novel silyl enol ethers. The ease of protecting group cleavage in these materials is manifested in the immediate formation of a strong latent image after exposure. High E_a polymers were prepared by introducing tertiary esters which contain the tris(trimethylsilyl)silyl group, and both methacrylate copolymers and norbornene-maleic anhydride copolymers containing this group have been synthesized. Both of these materials show good oxygen plasma etch resistance, with the latter demonstrating superior adhesion to poly(4- vinylphenol) planarizing layers. The tris(trimethylsilyl)silyl group imparts a high degree of hydrophobicity to coatings of many of these materials. Acid- catalyzed deprotection of these tertiary esters affords the corresponding carboxylic acids and 1-silyl-3-methylbutenes, and the liberation of these olefins is significantly faster than the loss of isobutylene from the tert-butyl analogs.

As critical dimensions for resist features shrink, resist roughness on the sidewall may contribute relatively more to the correspondingly smaller CD error budget. Thus, some photoresists may be more suitable than others for smaller dimensions. This paper compares and contrasts the sidewall roughness values measured by atomic force microscopy of two positive-tones, chemically amplified resists used in X-ray lithography.

The resist comprising naphthalene rings instead of benzene rings was developed for ArF excimer laser lithography. Naphthalene shows outstanding dry etch resistance, stronger adhesion to silicon surface and low hydrophobicity compared with most alicyclic compounds. Di-tert-butyl 2-[(1- adamanthyl) carbonylmethyl] (ADTB) was developed as an additive to improve the characteristics of development of base polymer. Although ADTB has tert-butyl protective groups, the decomposition temperature is low compared with that of polymer which has a tert-butyl protective group. Moreover, the dry etch resistance of the resist becomes greater as ADTB content increases. 0.133 micrometers L/S patterns were fabricated using Nikon's ArF prototype exposure system. Next, in order to improve the adhesion of the resist having the alicyclic frame, introduction of naphthalene in to the resist was attempted. The new resists which has naphthalene frame showed stronger adhesion and 0.15 micrometers L/S patterns were fabricated using the ArF exposure system with the standard developer.

A novel copolymer with alicyclic olefin moieties for an electron beam resist has been developed. In general, methacrylate copolymers widely used in the field of E-beam lithography show a low etch resistance due to their linear backbone structure. Our goal was to enhance an etch selectivity to various substrates while maintaining a high resolution. We designed alicyclic olefin copolymers with highly rigid backbone structures to improve the etch selectivity and synthesized a copolymer resin, poly(2- hydroxyethyl 5-norbornene-2-carboxylate/t-butyl 5- norbornene-2-carbolate/5-norbornene 2-carboxylic acid/maleic anhydride), which is formed with alicyclic units in their main chains. This alicyclic backbone structure of copolymer affords better etch selectivity to various substrates without sacrificing its resolution than those of other methacrylate copolymers. Etch selectivities have been studied for polysilicon, silicon dioxide, and tungsten substrates, respectively. Our resists showed the etch selectivities comparable to that of typical KrF resist for polysilicon substrate and comparable to those of typical novolac resist for silicon dioxide and tungsten substrates. The effect of photo acid generator to the electron beam lithographic performance was also investigated.

Protein patterns were printed using conventional microlithographic materials in a bilayer and a top DNQ/novolak layer. The protein features were printed in both 'contact printing', and 'step and repeat' mode. The latter printing mode can be managed in a single-cell, 'real time' process, as follows: (i) the exposure step is carried out in a cell by focused beam of a confocal microscope tuned to 488nm exposure; (ii) the development step is performed flowing the photoresist developer through the cell; (iii) the selective deposition of the protein is achieved via the flow of the protein solution through the cell until a desired contrast has been reached; (iv) the control step consists of an on-line monitoring of the red fluorescence for the control of the development of the top layer, and of the green fluorescence for the control of the protein patterning, respectively. The techniques have a seamless portability in a biomedical environment, and for 'step and repeat' protein patterning the advantage of a high and controllable resolution. The process can be applied in the fabrication of medical microanalysis devices.

The relation between the characters of the protecting groups and lithographic performance in chemically amplified resist was investigated by computational techniques. The stability of de-blocking reaction was estimated by means of molecular orbital calculation (MO). Their calculated results showed that electron withdrawing group increases the activation energy of de-blocking reaction. And the resists which contain these protecting groups were evaluated with acidic top-coating. Though the stability of de-blocking reaction correlated with the sensitivity of the resist, it was not necessarily effective to acidity of top-coating. Furthermore, we investigated the effect of the bulkiness and hydrophobicity of protecting groups to resist performance. As the bulkiness of the protecting group increased, the top shape of lines became better. However, without top coating, too bulky protecting group formed T-top shapes. These results show that the bulkiness of the protecting groups has relation to formation of the insoluble layer. The stabilization energy in the interaction of protecting groups with hydroxyl group of phenol ((Delta) H) was calculated by means of MO calculation. The highest value of (Delta) H between carbonate group and OH group is larger than that between acetal group and OH group by 1 kcal/mol. This result suggests that the interaction between carbonate group and OH of phenol contribute to the ability of dissolution inhibition.

We investigate the origin of the line-edge roughness (LER) of line patterns of chemically amplified photo resist for the purpose of reducing size fluctuations of patterns in present and future deep-UV lithography. An atomic force microscope analysis of the pattern sidewall reveals that there are tow kinds of roughness in the LER: short-range roughness with an average period of about 50 nm and long- range roughness with an average period of about 500 nm. The short-range roughness can be identified as polymer aggregates, which are essentially formed by the base polymer in the resist film. This is because the average period of the surface roughness due to polymer aggregates observed in the base polymer films is about the same as that of the short-range roughness. In addition, it is confirmed that aggregate extraction development occurs in the photoresist. On the other hand, the long-range roughness is generated not by the base polymer only but also by the exposure process because its average period increases with the exposure dose. The origin of the long-range roughness is also discussed.

We have examined a novel class of ketal based deep UV photoresist. 1,4-Dioxaspiro(4,4)nonane-2-methyl methacrylate was synthesized and polymerized. A ketal group of poly(1,4- dioxaspiro(4,4)nonane-2-methyl methacrylate) hydrolyzes under acid catalysis to give two alcohol functionalities and a cyclopentanone molecule. The ketal polymer is insoluble in an aqueous developer, while the hydrolyzed products are soluble.It was found the cyclopentanone product affects diffusion of acid in the resist. As a result, the generated cyclopentanone increases mobility of the acid significantly.

Inorganic resist such as amorphous alumina are projected as potential candidates for high resolution electron beam nanolithography; the drawbacks being its low sensitivity and tedious deposition process such as sputtering. Therefore, a spin-coatable Al₂O₃ resist with higher sensitivity is strongly desirable to overcome these drawbacks. In this paper, we describe the electron beam exposure characteristics of spin-coatable Al₂O₃ gel films prepared by reacting aluminium tri-sec-butoxide, Al(OBu^s)₃ with chelating agents like ethylacetoacetate. The electron beam sensitivity of approximately 70nm thick Al₂O₃ gel films baked at 40 degrees C as well as in the no-bake condition is approximately 4mCcm^-2, which is approximately 10⁶ times higher than the sputtered alumina films. Baking at 70 degrees C seems to produce little change in the sensitivity. The Fourier transformed IR spectroscopy studies indicate that the increased sensitivity of these films is due to the rapid breakdown of chelate rings under the electron beam. This rapid breakdown of organic bonds could have resulted in the appearance of inorganic Al-O bonds which are insoluble in acetone. Indeed the spin-coatable Al₂O₃ resist provides high resolution negative line patterns of linewidth of about 20nm.

Some of the important areas to be improved for lithography simulation are getting correct exposure parameters and determining the change of refractive index. It is known that the real and imaginary refractive indices are changed during exposure. We obtained these refractive index changes during exposure for 193 nm chemically amplified resists. The variations of the transmittance as well as the resist thickness were measured during ArF excimer laser exposure. We found that the refractive index change is directly related to the concentration of the photo acid generator and de-protected resin. It is important to know the exact values of acid concentration from the exposure parameters since a small difference in acid concentration magnifies the variation in the amplified de-protection during post exposure bake. We developed and used a method to extract Dill ABC exposure parameters for 193 nm chemically amplified resist from the refractive index change upon exposure.

We have been researching chemical changes that occur in positive-type photoresist within a recycling process. In this process, spin-coated photoresist is first collected together with the thinner used for washing the coated cup, and the diluted resists is then distilled. Next, by adding an appropriate amount of solvent, the viscosity of the resist is returned to its initial state. The resist is finally filtered and returned for use. Simulation experiments were performed using a spin coated. It was found that the photoresist takes on about 1 percent water content by absorbing moisture from the atmosphere during the spin- coating process, and that diazonaphthoquinone decomposes due to thermal stress, which is connected with a drop in photo- sensitivity. Accordingly, if the photoresist should happen to be free of water, and if heat should not happen to cause chemical changes in diazonaphthoquinone during refinement, sensitivity should not show a change in the extracted photoresist. With this in mind, it was decided that extracted photoresist must be refined in low-moisture conditions at low temperature. This photoresist recycling is therefore performed by refining photoresist at room temperature using equipment that can distill under reduced pressure. By adding fresh photoresist, this type of recycling can be continuously performed.

Although it is hard to strip away the photoresist layer damaged during the etching process in manufacturing liquid crystal display devices, monoethynoloamine (MEA) was found to have excellent photoresist stripping characteristics. Crosslinked novolak resin is easily dissolved in a MEA solution because MEA has a large cohesive energy, a strong affinity for novolak, and a small molecular weight. Pure MEA can be recycled with high yield by using a simple system that has short multiple-pipe distillation columns that have high heat-transfer efficiency. The pipes in our distillation system are made of 304 stainless steel because this material was found to resist corrosion in an aqueous MEA solution better than 316L stainless or Cu. This recycling system has been operating in production lines for more than two years without showing any signs of trouble.

In this paper we evaluate the photoactive compound (PAC) performance in a thick film photoresist. In an effort to report the performance of a thick film photoresist and the correlation to PAC structure, we have studied several formulations containing a monofunctional PAC(A) in comparison to a polyfunctional (PAC(B). We have seen that the use of a monofunctional photoactive compound provides for a high performance thick film photoresist with good profile, depth of focus, resolution, and exposure latitude. A polyfunctional PAC however, causes a loss in performance. The ratio of monofunctional PAC(A) to polyfunctional PAC(B) was varied and lithography was studied on a Nikon stepper (i-line). In our study, we evaluate the effect of the addition of PAC(B) to our formulations and the consequences in terms of lithographic performance.

We report the development of a novel acryl polymer with an (alpha) -hydroxymethyl acrylate in the application to 193nm chemically amplified negative-tone resist. This new polymer structure consists of ((alpha) -hydroxymethyl)acrylate and MAA. The ester and alcohol group in the polymer contribute to an intramolecule and/or intermolecular hybrid crosslinking reactions without crosslinker and in the presence of a photo generated acid as a catalysis. In an intramolecular crosslink reaction, the ester group reacts to a neighboring hydroxymethyl group within the polymer chain. As a result, a lactone group is made in the main polymer chain. On the other hand, in an intermolecular crosslink reaction, the ester group reacts to a hydroxymethyl group of another polymer chain to make an ester chain. In this reaction, the new polymer is densely crosslinked and fine resist pattern is obtained without having any swelling problem. Consequently, the resist is optimized and contains the new polymer, photoacid generator and a small amount of crosslinker. Under conventional illumination condition, 180nm line and space pattern are achieved without any kind of swelling problem. The sensitivity is 40 mJ/cm² with the standard developer, NMD-3 2.38 percent.

The trend toward narrower linewidths in the manufacture of integrated circuits has put an ever increasing burden on contamination control in every aspect of semiconductor fabrication. The number of microlithographic steps used in the fabrication of an integrated circuit has increased dramatically with the complexity of today's semiconductor chips. The removal of unwanted particle contamination from the photoresist before application to the wafer surface has been accomplished by filtration at the manufacturer of the photoresist as well as the end user. Metal ions in the photoresist now pose an ever increasing contamination problem with the feature sizes moving toward 0.25 micron and smaller. The removal of unwanted metal ions from the photoresist prior to application of the photoresists to the wafer surface will reduce device defects due to metal contamination. The introduction of a metal ion removal device to reduce the final metal ion content of photoresists will drastically reduce the exposure of the wafer surface to these contaminations. The reduction of metal ion concentration from several hundred ppb to single digit ppb will be demonstrated in single pass application of this device. Utilization of this technology will reduce the incidence of defects during the fabrication of the integrated circuit.

In a variety of microlithographic applications the importance of thick film photoresist continues to grow. Thick film photoresists are evolving into materials, which can meet the demand for smaller features while maintaining good exposure latitude, depth of focus, sidewall profiles, and photospeed. It is know that the performance characteristics of photoresists will change with changing process conditions and that the best performance of a photoresist is achieved by optimization of these conditions. One of the more critical steps in the lithographic process is development, which requires a tight process control. In our study we evaluated the effects of developer temperature and developing mode such as spray, spray/puddle, and immersion. The performance of an advanced thick film photoresists was examined regarding to resolution, depth of focus, exposure latitude, profile, photospeed, and scumming. A full lithographic evaluation was carried out. Assessment of the thick film photoresist, which is a commercially available product, was done on a Nikon. This paper includes a discussion, looking at the best compromise of performance based on temperature and develop process.

Organic anti-reflective coatings (ARCs) continue to play an important role in semiconductor manufacturing. These materials provide a convenient means of greatly reducing the resist photospeed swing and reflective notching. In this paper, we describe a novel class of ARC materials optimized for lithographic applications using 193 nm exposure tools. These ARCs are based upon polymers containing hydroxyl-alkyl methacrylate monomers for crosslinkable sites, styrene for a chromophore at 193 nm, and additional alkyl-methacrylate monomers as property modifiers. A glycouril crosslinker and a thermally-activated acidic catalyst provide a route to forming an impervious crosslinked film activate data high bake temperatures. ARC compositions can be adjusted to optimize the film's real and imaginary refractive indices. Selection of optimal target indices for 193 nm lithographic processing through simulations is described. Potential chromophores for 193 nm were explored using ZNDO modeling. We show how these theoretical studies were combined with material selection criteria to yield a versatile organic anti-reflectant film, Shipley 193 G0 ARC. Lithographic process data indicates the materials is capable of supporting high resolution patterning, with the line features displaying a sharp resist/ARC interface with low line edge roughness. The resist E_o swing is successfully reduced from 43 percent to 6 percent.

Shipley MICROPOSIT LOL lift-off technology exploits a develop rate difference in a resist, LOL1000 bi-layer system to generate retrograde profiles. This is an enabling technology for 'additive' processing. Deposition follows lithography and the resist is then 'lifted off' to generate a patterned layer.

Process simulation is necessary to investigate possible enhancements of some selective resist performance properties as a result of changes in the developer concentration. Accurate dissolution parameters are needed for different developer normalities to simulate their effect on the resist dissolution rates. Only qualitative similarities are observed in the dissolution behavior of similar chemistry based resist as a function of developer normalities. Quantitative differences in the dissolution rates and curve shapes are detected between resist based on different chemistries. No single universal dissolution model capable of describing the behavior of all different resists was found. However, individual resist dissolution/developer concentration models can be constructed.

This paper describes the formulation robustness of an 'ESCAP' type resist based on hydroxystyrene/t-butyl acrylate copolymer. The resist formation matrix consists of the polymer, a photo acid generator (PAG) and a base. The performance of the resist design was tested lithographically over 900 angstrom DUV-30 BARC as a function of variations in the PAG concentration and the base ratio to the PAG. The post exposure bake (PEB) temperature was also investigated as a third process variable in addition to the first two formation variables. The analysis of the results shows high performance tolerance to the formation variables. The resolution, focus latitude and exposure margin exhibited high tolerance to changes in the PEB temperature, PAG or base ratios.

Although the line-edge roughness of resist patterns is becoming a serious problem as the size of resist patterns are decreased, quantitative analysis has rarely been seen so far. We investigate the line-edge roughness of ArF resist patterns using the FFT method. We found that all the observed line-edge roughness had a specific FFT spectrum shape composed of a flat area at low frequency and a 1 (root) f component area at high frequency. The amount of line-edge roughness is independent of dose and linewidth but has a strong dependence on defocus. The patterns formed using TSI also have similar FFT spectrum shapes. Based on these findings, we proposed a line-edge roughness simulation method that achieves the observed FFT spectrum.

The use of di-functional monomers such as 2,6- Bis(hydroxymethyl)-p-cresol has allowed the design of novolak resins having alternating architecture with enhanced o,o'-bonding order, specific end-groups and narrow molecular weight distribution. When compared with a conventional m-/p- cresol formaldehyde novolak, the new resins have a lower molecular weight and molecular weight distribution with no p-cresol enriched oligomer fractions. Generally, these resins are used without further processing. With the proper monomer selection novolak resins can be made with the appropriate hydrophilic balance and dissolution characteristics essential for advanced resist development and optimization. By coupling the resin properties with the properties of diazonaphthoquinone sulfonate esters that have a high resolution potential, two advanced sub 0.25 micrometers i- line resist prototypes were developed. With annular illumination, Resist Prototype I demonstrated excellent linear resolution of 0.22 micrometers and an exceptional focus latitude of 1.4 micrometers and 1.7 micrometers for the 0.23 micrometers and 0.25 micrometers dense L/S, respectively; while Resist Prototype II showed linear resolution of 0.18 micrometers L/S and outstanding focus latitudes of 1.6 micrometers and 1.7 micrometers for the 0.21 micrometers L/S and the 0.23 micrometers L/S, respectively.

Negative tone chemically amplified i-line resists possess several advantages compared to conventional DNQ-Novolak resist. These advantages include excellent lithographic performance at a fast, tunable photospeed, high transparency, high thermal flow stability and improved etch resistance. An additional advantage of using negative resist of logic applications is that the difference in CD for various features at a fixed dose is small relative to conventional positive resists, allowing the maximum potential for printing these features simultaneously. ULTRA- i 300/310 are negative acting i-line photoresist with excellent lithographic performance optimized for 90 degrees C PAB/110 degrees C PEB processing. These materials offer extremely high resolution capability without microbridging, fast photospeed, and a robust post exposure delay process window with minimal film loss over a period of hours. these resists exhibit extremely low PEB temperature sensitivity which is expected to reduce across chip linewidth variation. Low optical density permits thick film applications producing high aspect ratio relief images with vertical profiles. Furthermore, addition of appropriate dyes permits resists to be designed for lift-off applications with controlled retrograde profiles.

Some of the major limitations of top surface imaging schemes are now well documented: critical dimension (CD) control across the wafer can be a serious issue as well as line edge roughness (LER). A primary focus of our work has been to investigate the performance of the 248 nm bi-level negative tone approach of the CVD photoresist process based on the plasma polymerization of methylsilane. In this paper, CD control data within a field and across the wafer are presented. CD control is shown to be very strongly dependent on the uniformity of the development step. The best results are obtained when using straight chlorine for the plasma etch development step.

Line end shortening is a phenomenon originating from a combination of imperfect aerial image formation of the line end and acid diffusion in chemically amplified resists. For geometries at 0.25 micrometers and below, line end shortening has become a concern in photolithography. Because of the complex coupling between the optical effect and the acid diffusion, accurate and reliable prediction of line end shortening form theory is difficult. Experimental characterization of line end shortening is thus required. In this study, line end shortening was measured on OPAL CD SEM using a special measurement algorithm. Our experimental results show that both NA and (sigma) affect line end shortening, higher (sigma) are preferred to reduce line end shortening. PEB time has little effect on line end shortening, while line end shortening increases with PEB temperature only when it reaches a chemical mechanism transition temperature. The most effective way to minimize and control line end shortening is through optical proximity correction. By optimizing the serif size, not only the desired line end dimension can be achieved, but also its process latitude is greatly improved.

In chemically amplified resists, acids are generated upon DUV illumination. What DUV illumination really creates is an electrolyte solution with non-uniform acid distribution. Since H⁺ carries a charge, its diffusion behavior is quite different from that of a neutral particle. The long range Coulomb interaction between charged particles can be very important in a medium with low dielectric constant such as resist. The diffusion of acid and its counter ion are strongly correlated, leading to a decrease of the effective diffussivity of acid. Detailed theoretical analysis shows that the diffusion coefficient that determines the critical dimensional change caused by acid diffusion is the effective acid diffusion coefficient D_a equals 2D_x, which is determined by the diffusivity of the counter ion. The diffusion coefficient that is related to chemical amplification is the acid intrinsic diffusion coefficient D_H+. The charge carried by H⁺ also makes its evaporation difficult due to large energy barrier created by electric potential difference between two phases and the 'image force' when H⁺ crosses over the resist/air rate depends on the acid diffusivity, acid strength and acid equilibrium vapor pressure at the post exposure bake temperature from the kinetic theory.

The structural influence of photoacid generators on DUV resists performance is investigated in both high and low activation energy resists system. The lithographic behaviors of the photoacid generator is considered in terms of the structure of the photogenerated acid and the light sensitive chromophore. First, the lithographic impact of the photogenerated acid is investigated in terms of acid strength and acid size in resists optimized for high and low temperature processing, respectively. Dissolution kinetics, contrast curve data and absorbance data are presented for a series of high and low activation energy resists in which the structure of the photogenerated acid is systematically varied. The results of these studies are discussed in terms of the photogenerated acid, emphasizing the impact of acid strength and size on lithographic performance and resists dissolution rate kinetics for each resists platform. Secondly, the structural influence of the light sensitive PAG chromophore is investigated by comparing the lithographic performance and dissolution rate kinetics are probed in terms of resist type and PAG structure.

This paper presents the chemistries and properties of organic, spin-on, bottom antireflective coatings (BARCs) that are designed for 193 nm lithography. All of the BARCs are thermosetting and use dye-attached/incorporated polymers. A first generation product, NEXT, will soon be commercialized. NEXT is built form i-line and deep-UV chemistries with the polymeric constituent being a substitute novolac. This product provide outstanding resolution of 0.16 micrometers L/S with several 193 nm photoresists. Second generation chemical platforms under study include acrylics, polyesters, and polyethers with the 193 nm absorbing chromophore being an aromatic function. The performance of selected BARCs from the four platforms is described, including: optical properties, 193 nm litho, plasma etch rates, Prolith modeling data, spin-bowl and waste line compatibility, and ambient stability.

The goal of this paper is to define a 'state of the art' of the lithographic performance obtained with an advanced 193 nm single layer resist process, for 150 nm technology generation specification and below. Even if the goal of the paper is not to propose a process ready to be implemented in pilot lines, the resist used should be commercially available and exhibit good performance. The Sumitomo PAR101 A4 meets both criteria and is selected for the study. In order to get the best performance from the resist, all evaluation work is completed using a BARC. Both inorganic and organic materials are first considered; their processes are optimized to obtain the best reflectivity control and chemical compatibility with the resist. Then, using G0, conventional illumination and a binary reticle, the process performance is evaluated in terms of linearity, depth of focus, energy latitude and proximity effects for 150 nm and 130 nm lines, and depth of focus and energy latitude for 170 nm contact holes. Different optical extension techniques are then compared for increasing the 130 nm lines process latitudes: off-axis illumination, and alternating phase shift masks.

It is generally known that a highly transparent ArF resists is preferable for the bottom ARC process to maintain the vertical sidewall of resist patterns. Therefore we developed some transparent resists with a low concentration of photo acid generator. However, our careful analysis clarified that the completely transparent resist caused a serious deterioration of the exposure-defocus (E-D) process window. Therefore, there should be an optimum transparency in the ArF resists. Our experiment clarified that the medium transparency resists had the largest E-D process window. This resist produced 120 nm nested lines using an ArF stepper without any resolution enhancement technique.

In this paper, commercially available DUV resist for 'thick' resist applications were used to study the chemical and processing aspects of thin imaging layers. Two types of resist were used: a high Rmin resist and a low Rmin resist, both from Shipley. Input parameters were process conditions such as soft bake, post-exposure bake and development time. Also the influence of the resist thickness was taken into account. Output parameters are contrast, profiles and process windows. The most important parameters for optimizing thin imaging layers are Rmin and the post- exposure bake.

A systematic approach was taken in order to improve the planarity of a DUV anti reflectant (AR) utilized for various lithographic steps, particularly those involving a patterned transparent layer. These layers can occur in both front and back end processing. Two approaches were pursued to accomplish this. The first approach was to minimize the molecular weight of the AR polymer. Polymers with weight average molecular weights from 45,000 daltons to as low as 2,300 daltons were evaluated. The planarity of the AR improved significantly for polymers with Mw's below 20,000 daltons. The second approach was to add plasticizers in order to reduce the glass transition temperature of the precrosslinked film. The addition of plasticizers to the AR was effective in increasing the planarity. One of the plasticizers contained a DUV chromophore used to maintain the required optical density of the AR. It was proven possible to make these changes while maintaining lithographic performance in both resist profiles and reflection control.

Traditional methods of measuring the Dill C Parameter involve monitoring the absorbance of a resist as a function of exposure. In chemically amplified resist, absorbance changes with exposure are small and frequently have little correlation to the amount of photoacid generated.

This paper present a methodology for modeling and simulating line-end shortening (LES) effects in deep-UV photoresist and calibrating the simulation with experimental data. A reaction/diffusion mode is first calibrated using large area dose-to-clear versus bake time data and thickness loss from a top-to-top bake experiment. SPLAT and STORM are linked to simulate the exposure and post exposure bake processes of chemically amplified resist. A threshold mode is then applied to determine the line-end shortening effects. Verification experiments were conducted on two resists, APEX-E and UVIIHS, for several types of geometric features, and the resist model parameters were fine tuned using the Method of Feasible Direction. The measurement of LES agrees quite well when the simulation using an exponential diffusion model of post exposure bake is used. The fine tuning reduced the RMS error to below the noise level in the experimental data and improve the accuracy in predicting LES to 10 percent of feature size.

This paper describes the development of a lithographic model for Shipley UV6 DUV photoresist from fundamental materials constants. Parameters describing optical absorbance, acid generation, acid generation, acid diffusion, resin deprotection, and resists dissolution rate were measured and input into PROLITH/2. Initial simulations showed significant deviations from observed lithographic performance. Simulated E₀ swing curves showed a large bulk effect absent in experiment data. Simulated lines showed excessive top loss and tapering which were corrected by the artificial introduction of a surface base contaminant. Lithographic process windows for lines and contacts cold be successfully simulated after considerable adjustment of the acid diffusion coefficient and development parameters, but accurate simulation of both profile and process window with a single set of parameters was only possible for contacts. The manipulations required to match simulated and experimental data did lead to some insights into resists materials design. Simulations suggest that lowering acid diffusion should increase exposure latitude and reduce film thickness loss, while suppressing the resist dissolution rate at the onset of deprotection should improve both focus and exposure latitude.

Thin film imaging processes such as top surface imaging (TSI) are candidates for sub-150 nm lithography using 193 nm lithography. Single component, non-chemically amplified, positive tone TSI photoresists based on phenolic polymers demonstrate good post-etch contrast, resolution, and minimal line edge roughness, in addition to being the most straightforward thin film imaging approach. In this approach, ArF laser exposure results directly in radiation- induced crosslinking of the phenolic polymer, followed by formation of a thin etch mask at the surface of the un- exposed regions by vapor-phase silylation, followed by reactive ion etching of the non-silylated regions. However, single component resists based on poly(para-hydroxystryene) (PHS), such as MicroChem's Nano MX-P7, suffer from slow photospeed as well as low silylation contrast which can cause reproducibility and line-edge-roughness problems. We report that selected aromatic substitution of the poly(para- hydroxystryene) polymer can increase the photospeed by up to a factor of four relative to un-substituted PHS. In this paper we report the synthesis and lithographic evaluations of four experimental TSI photoresists. MX-EX-1, MX-EX-2, MX- EX-3 and MX-EX-4 are non-chemically amplified resists based on aromatic substitutions of chloro- and hydroxymethyl- groups and PHS. We report optimized lithographic processing conditions, line edge roughness, silylation contrast, and compare the results to the parent PHS photoresist.

Lithographic conditions are typically optimized for a specific feature type; while some levels expose lines and spaces, others target contacts and islands. In today's challenging lithographic environment, printing multiple feature types on the same reticle is being discussed. The overlapping process window must then be considered. It is well-established in the industry that, for DNQ systems, two dimensional structures print at different doses than one dimensional structures of the same nominal chrome or clear size on the reticle. In this paper, the overlapping or common process window for all of these features is examined using a state-of-the-art i-line negative photoresist. When evaluating depth of focus (DOF) and exposure latitude, a +/- 0.10 micrometers deviation from target was used. Contact holes consistently limited the common process window. Three illumination conditions were examined: 0.57 NA with 0.38 sigma, 0.57 NA with 0.67 sigma, and 0.60 NA with 0.38 sigma. For total common process window, the 0.57 NA and 0.38 sigma condition was found to be optimal. PROLITH/2 aerial image simulations were found to agree with experimental result regarding an increased common exposure latitude with high NA and low sigma. The nominal feature dimensions were: 0.44 micrometers isolated lines, 0.44 micrometers isolated spaces, 0.4 X 1.5 micrometers contact,s and 0.4 X 1.5 micrometers islands. The nominal dimensions for contacts and islands were chosen to maintain a 3:1 area rule should the minimum dimension be used for one side of the features. The importance of a minimum area rule is discussed. Some early work on a second i-line negative resist targeted to simultaneously print 0.30-0.40 micrometers lines and spaces with 0.35-0.50 micrometers ² contacts and islands is mentioned.

State-of-the-art microlithographic processes used to make features smaller than 0.25 microns are based upon deep-UV lithography and chemically amplified resists (CARs). In these resists, photoacid generated during exposure initiates cascading deprotection reactions during post exposure bake (PEB) to form a developable image. Reaction may not be limited to the illuminated areas since the photo-generated protons may diffuse outside this region; therefore, it is important to understand the diffusional characteristics of the photoacid. In this contribution, the photoacid generation during exposure was characterized using acid- sensitive fluorescence of fluorescein, and the acid mobility and concentration during PEB were studied using crystal violet. These probes were added to the Shipley Apex-E 2408 DUV photoresist, and measurements were carried out in situ on quartz substrates. For fluorescein, characteristic changes in the fluorescence peaks intensities were used to determine the acid concentration during exposure. Crystal violet is a triphenylmethane 'propeller' molecule whose excited state lifetime increases as the local free volume decreases, and molecular rotation is hindered. This feature can be used to characterize the free volume in the photoresists using ground state recovery experiments. In addition, crystal violet has three protolytic forms, each with a unique absorption spectrum, and calibration of the absorption spectrum as a function of acid concentration was used to measure the acid concentration during PEB. These studies illustrate the utility of spectroscopic techniques based upon carefully selected molecular probes to characterize CARs in situ.

Multiple contact hole resist samples from a variety of DUV resist suppliers, including both acetal and ESCAP chemistries are evaluated on an organic anti-reflective under layer (ARC) using an attenuated phase shift mask (APSM). One sample exhibited excellent surface inhibition and superior lithographic performance for patterning contact holes of 0.2 micrometers imaging size. For most of resists, the process windows are limited by unwanted sidelobe printing through focus. The sensitivity of sidelobe printing to focus can be attributed to lens aberrations. For the first time, we prose to use Depth-of-focus (DOF) loss PWL_dof and Exposure latitude (EL) loss PWL_el to characterize resists surface inhibition, as well discovered that DOF loss is a sensitive measure of surface inhibition. Similar lithographic performance is obtained from acetal and ESCAP based materials. The two ESCAP resists EB3 and EA2 have better oxide etch resistance than the acetal resist AC1. The top surface reticulation is observed on ESCAP resist EB3 and EA2 during the oxide etch, but not on the acetal resist AC1. 110 nm underexposed resolutions achieved with the resist EA4 at a mask size of 250 nm. Faster resists generally exhibit better resolution but have smaller process windows when side lobe printing is included as a criterion. Selection of a resist formulation for attenuated phase shift applications has to face a compromise between resolution, photospeed, process window and surface inhibition. Finally, ARC operational modes and optical properties had little effect on sidelobe printing, and optimization of PEB temperature is important in suppressing sidelobe printing.

A special UV curing process which employs an ammonia blanketing gas was investigated to determine if a reduction in chemically amplified photoresist loss cold be attained in oxide, polysilicon, and metal plasma etch processes. In addition, a reduction in film shrinkage was sought relative to curing processes, which do not employ a basic gas during the stabilization process. Representative commercially available 248 nm chemically amplified photoresists from the t-BOC, acetal, and ESCAP families were included in this study. These studies were limited to unpatterned resist films and were conducted with an H-mod bulb, having a wavelength cut-off of 250 nm. The parameters varied in this study included UV irradiation intensity, process time, and temperature. Film shrinkage, refractive index, FTIR spectral changes, dissolution properties in an alkaline developer, and etch rate properties in fluorocarbon and chlorine based plasmas were measured. It was demonstrated that the ammonia- based photostabilization process result in less film shrinkage than the corresponding process with no basic purge gas. Evidence is provided that cross linking result from the UV curing process. The photostabilization process has been optimized for a number of photoresists to minimize the film shrinkage resulting from photostabilization and to significantly reduce the plasma etch rate. Benefits are shown to be greater for low activation energy and t-BOC type resists.

To meet the technology needs at their insertion into integrated circuit manufacturing, the testing and development processes of 300 mm wafer compatible tools require imaging of 180 nm and smaller features. In response to this need, processes employing commercially available chemicals intended for use on 200 mm substrates and capable of producing 180 nm and smaller features were developed. Said processes were later used for examining critical dimension control on 300 mm wafers. The methods and the experimental designs used to optimize 300 mm coat, exposure, and develop processes for two positive acting, chemically amplified resist systems are described. A low activation energy resist, PEG-11A3, and a high activation energy resists, UV6, were coated on top of DUV42-6 anti-reflection layer. Results show both resist capable of 140 nm equal line and space processing layer. Results show both resists capable of 140 nm equal line and space processing with process window size limited only by phase errors of the alternating phase-shift mask that induce image placement problems.

This paper will evaluate the potential improvements with the addition of an aqueous based top antireflective coating to a Deep-UV process. This antireflective coating (ARC) is resistant to intermixing with the resists and is removed during the normal develop operation. A logic IC with 0.15- 0.18 micrometers design rules will be the primary test vehicle, concentrating on Contact/VIA levels. Performance will be compare with and without the top ARC. Uniformity of measured critical dimensions (CD) will be compared. CD/dose swing curve suppression, as a function of substrate and resist thickness, will be documented. The Deep-UV resist/top ARC application will be optimized, as well, to maximize throughput.

The need to make well characterized resins consistently is paramount to the preparation of high performance photoresists. Solid resins fractionated by selective precipitation have been separated by ultracentrifugation at varying temperatures. At sufficiently high revolutions per minute, solvents and oligomers are efficiently squeezed out leaving behind polymer with higher average molecular weight and lower dispersity than resins obtained by more common isolation techniques. By controlling isolation conditions, resins with desired dissolution rates could be produced. Lithographic test confirmed that resists properties could effectively be controlled by manipulation of process conditions to isolate resins used in the formulations.

A system for measurement of deprotection reaction parameters for use with chemically amplified (CA) resist was developed by incorporating baking equipment into a FTIR spectrometer. Using this system, studies were conducted of a new model based on previous deprotection reaction models, but including the effects of deprotection reaction delay and the presence of a quencher. Used in these studies were a t- BOC/PHS resist for KrF excimer laser exposure, and a TBMA_0.33-IBMA_0.33-MMA_0.33 copolymer resin resists for ArF excimer laser exposure. Deprotection reaction parameters for this model were measured for these two resist. The resulting parameters were then used with the PROLITH/2 lithography simulator for profile calculations, which were compared with SEM observations, general tendencies agreed quite well. This finding indicates that the present model may be reasonably applied to CA resists intended for KrF and ArF excimer laser exposure, and confirms the usefulness of the systems described for deprotection reaction parameter measurement.

The effects of developer temperature and developer normality on the dissolution behavior of a 248nm chemically amplified resist are examined using development rate measurements. Using a RDA-790 development rate measurement tool employing a 470nm Blue LED measurement wavelength, dissolution rats as a function of dose and depth into the resist were measured. Each data set was analyzed and the performance of rate versus t-BOC concentration was fit to appropriate models. The variation of these results with developer temperature has led to further temperature-dependent characterization of the dissolution modeling parameters. The variation of dissolution rate with developer normality has led to an initial characterization of the normality-dependent dissolution modeling parameters. The maximum dissolution rate R_max is shown to exhibit two regions of Arrhenius behavior with a well defined activation energy for both. The dissolution selectivity parameter n proves to have a more complicated behavior.

In order to increase the etch resistance of photoresists, patterned resist features are stabilized by UV/Bake process. This process provides increased etch resistance to the film by densifying the resist. It is understood that resists is crosslinked during the UV/bake process and as such, better crosslinked resist, typically have better plasma etch resistance. However, historical UV/bake curing of Deep UV resists can cause loss of Cd control because of the excessive shrinkage of the film. Resist shrinkage has been reported to be due to loss of free volume. A major source of free volume los in deep UV resists is the deprotection reaction and the evaporation of the protecting groups. A significant reduction in film shrinkage is observed in UV/bake curing of deep UV resist films under ammonia or other amine purge gases. It is known that deep UV chemically amplified resist, are sensitive to environmental contaminants such as ammonia and other amines resulting in 'T-topping' or other forms of image degradation. However, during the UV/bake curing of deep UV resist images, under amine purge, it appears that the amines act to neutralize the photogenerated acid, thereby preventing the deprotection of the acid labile groups, and thus, results in a significant reduction in shrinkage. In this paper we demonstrate that the major role of amines in shrinkage reduction, during the UV/bake cure process, is not entirely prevention of deprotection of the acid labile groups alone. An additional mechanism is proposed to explain further significance of ammonia and other amines in film shrinkage reduction during the UV/bake cure process.

The newly developed AZ BARLi II coating material is a photoresist solvent-based bottom antireflective coating (BARC) for i-line lithographic application. The coating material has good compatibility with common edge bead removal solvents such as ethyl lactate, PGME, or PGMEA mixed with ethyl lactate or PGME. To evaluate the BARC material, its chemical compatibility with common EBR solvents has been tested by several analytical techniques including liquid particle counts and surface defect studies. Both top and bottom EBR dispense processes have been investigated and optimized. Improvements on edge roughness, visual cleanliness, and the BARC coating buildup at the edge will be discussed in this paper.

We have recently developed a bilayer resist system based on a methacrylic silicon-containing imageable layer and a UV curable copolymer undercoat which has exhibited 0.13 micrometers resolution for dense features and 0.12 micrometers resolution for isolated features after substrate etch. In this paper, we will discuss recent advancements in the design of the second generation bilayer resist. In particular, we will discuss the development of two new thermally curable undercoats for use in both 193 nm and 248 nm applications. The optical properties of these new materials have been optimized to reduce reflectivity at the desired wavelength.

Recently, base additives have become indispensable ingredients in high resolution chemically amplified resists. These bases act as acid scavengers to extend shelf life for low activation systems such as ketal and acetal protected polyhydroxystyrene type rest. They are also used to improve contamination resistance for high activation resist system such as TBOC and t-butyl ester containing resins. Studies have also shown that base additives can reduce linewidth slimming and PEB sensitivity for acetal systems. Actually, one of the most important benefits of base additives is to limit acid diffusion and enhance chemical contrast during exposure and bake process, hence improving resolution and process latitudes. In this paper, we show that polymeric bases provide better litho performance than small compounds. In addition, hydroxides are found to be better than carboxylate salts and amines.

E-beam lithography has recently emerged as a critical technology for the future semiconductor industry in the aspects of mask making, direct write and projection printing. Complexities in phase shifted and optical proximity corrected mask fabrications require high resolution, thermal bake insensitivity and RIE etch resistance. Direct write and projection also need high speed to address the throughput issue. These stringent requirements have rendered chemically amplified resists the strong candidates for the next generation E-beam lithography. Previously, we reported on a methoxypropene protected polyhydroxystyrene (PHS) system as a high performance chemically amplified E-beam resist. This system required weak aqueous base developer and was more sensitive to high temperature bake. The need for higher thermal stability to endure high temperature device fabrication process has prompted us to investigate other protecting groups. Benzyloxypropene protected PHS resist system was one of the earliest systems investigated. 100nm Cu lines fabricated with this resist formation through metallization, Damascence and lift off process have been demonstrated. In this paper, we will discuss the chemistry and properties of this resist system in conjunction with its E-beam lithography and metallization application.

As the feature size in microlithography decreases in response to the demand for increasing miniaturization, problems related to acid diffusion and acid loss become more important. In an attempt to address these issues, we have examined various techniques based on absorption and fluorescence spectroscopy. We have synthesized, or developed for applications in this field a range od dyes where their absorption and fluorescence change dramatically as a result of acid-induced changes in their prototropic forms. These dyes represent the basis for an in situ method for quantifying acid in films. Approaches for monitoring acid movement into/out of films have been developed and rate constants for acid loss from poly(vinylphenol) films of various acids at different temperatures have been determined. In an approach to measure acid diffusion, we make use of the fact that fluorescent patterns produced by contact printing of polymer films containing a dye can be readily resolved by fluorescence microscopy and that diffusion leads to deterioration of these images. In yet another approach, we have used laser photolysis techniques with nanosecond-microsecond resolution to generate acid photochemically and monitor on short time scales its arrival to dye-containing sites within the polymer films. The advantages and disadvantages of each technique will be discussed, as well as the role of acid, polymer Tg and temperature on acid diffusion/loss.

In the manufacture of many types of integrated circuit and thin film devices, it is desirable to use a lift-of process for the metallization step to avoid manufacturing problems encountered when creating metal interconnect structures using plasma etch. These problems include both metal adhesion and plasma etch difficulties. Key to the success of the lift-off process is the creation of a retrograde or undercut profile in the photoresists before the metal deposition step. Until now, lift-off processing has relied on costly multi-layer photoresists schemes, image reversal, and non-repeatable photoresist processes to obtain the desired lift-off profiles in patterned photoresist. This paper present a simple, repeatable process for creating robust, user-defined lift-off profiles in single layer photoresist using a non-thermal electron beam flood exposure. For this investigation, lift-off profiles created using electron beam flood exposure of many popular photoresists were evaluated. Results of lift-off profiles created in positive tone AZ7209 and ip3250 are presented here.

'On-chip' color filters are commonly used to convert monochromatic, solid-state image sensor into color sensors because they offer a good compromise between cost and resolution for digital cameras. The color filters are fabricated directly onto the surface of the CMOS or CCD image sensors, which generates a mosaic array of pixel-size filter elements. Diazonaphthoquinone-novolak photoresist is used to produce these filters by successively depositing and patterning each color layer. The choice of colors can vary from additive to subtractive or combinations of both.

Silicon oxynitride has been shown to be an efficient antireflective materials at 365 and 248 nm. In this paper, we confirm that SiON can be used successfully at 193nm. SiON is deposited at low substrate temperature in a Plasma Enhanced Chemical Vapor Deposition reactor using silane and nitrous oxide as precursor gases. Compatibility of the silicon oxynitride underlayer with sensitive chemically amplified resist is examined. A simple surface treatment is shown to give very good results and almost completely suppresses any contamination of the chemically amplified resist.

The development and refinement of 193 nm single layer photoresist has continued to progress at a quick pace. Published resists efforts have historically been partitioned by polymer family: acrylic, addition cyclic olefin, and alternating cyclic olefin/maleic anhydride. The polymer platforms for 193 nm resists have been a radical departure from 248 nm resists, therefore, publications to date have largely focused on the attributes of each specific variety. Since the physical and chemical properties of the aforementioned polymer platforms are very different, it would follow that, in principal, typical formulation strategies should produce varying results in each platform. This paper investigates the effects of three typical photoacid generators and three model polymers on various aspects of lithographic evaluation.

Understanding and control of molecular weight-dependent properties of 193 nm photoresist polymers has received only limited attention to date. Many physical and thermal properties of polymers in general and novolak- and poly(hydroxystyrene)-based systems in particular are molecular weight dependent. Since these properties markedly influence photoresist behavior, a more detailed understanding of molecular weight effects in 193 nm polymers would be valuable. In this communication, we present a survey of some of the interplays between molecular weight, thermal properties, dissolution behavior, and lithographic performance of methacrylate-based 193 nm polymers. More specifically, this presentation comprises a discussion of discontinuities in thermal properties surrounding the polymer critical entanglement molecular weight in methacrylate 193 nm polymers including the IBM Version 2 and Version 3 platforms. T_g vs. molecular weight curves for both platforms are in good agreement with predictions of the Gibbs-DiMarzio model and reveal that M_crit is ca. 8,000 for these systems. Lithographic characterization at, below, and above this molecular weight reveals failure due to fraying and line collapse at low molecular weight, failure due to excessive bottom scumming at high molecular weight, and best performance at or near M_crit.

For a range of thick film photoresist applications, including MeV ion implant processing, thin film head manufacturing, and microelectromechanical systems processing, there is a need for a low-temperature method for resist stabilization and curing. Traditional methods of stabilizing or curing resist films have relied on thermal cycling, which may not be desirable due to device temperature limitations or thermally-induced distortion of the resist features.

This study investigates resist stabilization techniques as they are applied to a metal etch application. The techniques that are compared are conventional deep-UV/thermal stabilization, or UV bake, and electron beam stabilization. The electron beam tool use din this study, an ElectronCure system from AlliedSignal Inc., ELectron Vision Group, utilizes a flood electron source and a non-thermal process. These stabilization techniques are compared with respect to a metal etch process. In this study, two types of resist are considered for stabilization and etch: a g/i-line resist, Shipley SPR-3012, and an advanced i-line, Shipley SPR 955- Cm. For each of these resist the effects of stabilization on resist features are evaluated by post-stabilization SEM analysis. Etch selectivity in all cases is evaluated by using a timed metal etch, and measuring resists remaining relative to total metal thickness etched. Etch selectivity is presented as a function of stabilization condition. Analyses of the effects of the type of stabilization on this method of selectivity measurement are also presented. SEM analysis was also performed on the features after a compete etch process, and is detailed as a function of stabilization condition. Post-etch cleaning is also an important factor impacted by pre-etch resist stabilization. Results of post- etch cleaning are presented for both stabilization methods. SEM inspection is also detailed for the metal features after resist removal processing.

With the integration of high current ion implant processing into volume CMOS manufacturing, the need for photoresist stabilization to achieve a stable ion implant process is critical. This study compares electron beam stabilization, a non-thermal process, with more traditional thermal stabilization techniques such as hot plate baking and vacuum oven processing. The electron beam processing is carried out in a flood exposure system with no active heating of the wafer. These stabilization techniques are applied to typical ion implant processes that might be found in a CMOS production process flow. The stabilization processes are applied to a 1.1 micrometers thick PFI-38A i-line photoresist film prior to ion implant processing. Post stabilization CD variation is detailed with respect to wall slope and feature integrity. SEM photographs detail the effects of the stabilization technique on photoresist features. The thermal stability of the photoresist is shown for different levels of stabilization and post stabilization thermal cycling. Thermal flow stability of the photoresist is detailed via SEM photographs. A significant improvement in thermal stability is achieved with the electron beam process, such that photoresist features are stable to temperatures in excess of 200 degrees C. Ion implant processing parameters are evaluated and compared for the different stabilization methods. Ion implant system end-station chamber pressure is detailed as a function of ion implant process and stabilization condition. The ion implant process conditions are detailed for varying factors such as ion current, energy, and total dose. A reduction in the ion implant systems end-station chamber pressure is achieved with the electron beam stabilization process over the other techniques considered. This reduction in end-station chamber pressure is shown to provide a reduction in total process time for a given ion implant dose. Improvements in the ion implant process are detailed across several combinations of current and energy.

With the integration of high energy ion implant processes into volume CMOS manufacturing, the need for thick resist stabilization to achieve a stable ion implant process is critical. With new photoresist characteristics, new implant end station characteristics arise. The resist outgassing needs to be addressed as well as the implant profile to ensure that the dosage is correct and the implant angle does not interfere with other underlying features. This study compares conventional deep-UV/thermal with electron beam stabilization. The electron beam system used in this study utilizes a flood electron source and is a non-thermal process. These stabilization techniques are applied to a MeV ion implant process in a CMOS production process flow.

Novolak resins fractionated using a unique method, were compared to resins fractionated with conventional methods. The potential for improving the fractionation/separation process and for making improved or more consistent resist with the resins was identified. Several experimental designs were run to determine optimum conditions needed to achieve better separation. Isolated resins were used to make experimental i-line photoresists which were tested against resists made with the conventional processes.

Low polydispersity novolak resins were prepared in a sequential process where low molecular weight (Mw) oligomers were first synthesized in a preliminary stp followed by a second condensation with preformed bis-hydroxymethyl derivatives of phenolic starting materials. Resins prepared in this way were found to have polydispersities comparable to that of fractionated resins made in the standard resin synthetic process. The sequential process afforded higher yields of usable resins since no low Mw fractions were isolated and discarded. In several instances, unique bis- hydroxymethyl phenol monomers or monomer/dimmer mixtures were prepared for use in making the low dispersity resins. These compounds were further condensed with the products of the initially prepared low Mw resins in a second acid catalyzed condensation.

Several novel norbornene carboxylate monomers consisting of isobornyl and alkyl ether chains on the ester groups were synthesized and polymerized with maleic anhydride (MA), t- butylnorbornene carboxylate (BNC), hydroxyethylnorbornene carboxylate (HNC) and norbornene carboxylic acid (NC). These polymers were compared with BNC/HNC/NC/MA tetra-polymers with respect to glass transition temperature (Tg) as well as photoresist performance using a 193 nm exposure tool. It was observed that introduction of these groups decreases the Tg but not to the extent where the polymers can be used as an annealing type resist. The synthesis of these polymers, their characterization, and their lithographic evaluation as 193 resists will be discussed in this paper. Further optimization in terms of final polymer composition as well as resist formulation is on-going in order to fully exploit these monomers for photoresist application.

In our previous publication we reported an improved process for isolation of novolak resins form phenol-formaldehyde condensation mixtures. The process results in resins having low polydispersity and slow photospeed. Novolak resins were prepared by the same process, employing different ratios of the cresol components. This paper will discuss an experimental design analyzing relationship between cresol component ratios and properties of the resins. The characteristics of the resins and their effect on the lithographic performances as an i-line photoresist composition will also be discussed.

The morphology and degradation of the polymeric DUV resist of polyhydroxystyrene/t-butyl acrylate copolymers after CF₄/O₂/Ar/CHF₃ reactive ion etching (RIE) was studied. The surface pitting in the area of 10 nm with spikes as large as 85 nm were found. DUV resists with higher t-butylacrylate content in the main chain were susceptible to main chain scission and surface pitting. The entrapment of volatile fragments by the deposited amorphous fluorocarbon polymer during the RIE process leads to surface distortions. Pre-hardening of the resist by electron beam reduces the surface pitting by two fold. Negative resist based on polyhydroxystyrene homopolymer with minimum volatile produced very smooth films with a tenfold reduction in roughness factor. The future design of positive resist should include the RIE performance factor of minimal outgassing and minimum sidewall surface roughness.

The demand for smaller and more uniform features on photomasks is rapidly increasing. The complexity of these patterns is also increasing with the need for optical proximity correction and phase shifting structures. These complex mask features demand unprecedented accuracy in pattern placement and dimensional control. We have conducted research designed to optimize the process for laser pattern generation by improving resolution and process latitude. Lithographic simulation was utilized for process optimization because of the very high cost of mask patterning and metrology experiments.

An efficient software tool, STORM, is described for simulating 2D line-edge profiles and line-end shortening in chemically-amplified resist (CARs). The most difficult aspect of modeling CARs is emulating the amplification reaction and reaction state dependent transport. The difficulty arises primarily out of the nonlinearity associated with the behavior of diffusion with reacted materials state. These phenomena have important impacts in horizontal and vertical cross section profiles of post- exposure baked resists. They also impact line-ends which are three dimensional but may be approximated using the two horizontal dimensions.

Dye compounds are commonly used in photoresists as a low cost and effective way to control swing and/or standing wave effect caused by thin film interference as well as reflective notching by reflective light from highly reflective substrate and topography. Convention dyes are typically a monomeric compound with high absorptivity at the wavelength of exposure light and compatible with the resist system selected. Because of the monomeric nature, conventional dyes are relatively low in molecular weight hence their thermal stability and sublimination propensity has always been an issue of concern. We recently synthesize several highly thermal stable diazotized polymeric dyes. Their thermal properties as well as compatibility with resist system were investigated. The impact of polymeric dyes on the resists lithographic performance, swing reduction and reflective notching control are discussed.

In this paper, we present the synthesis, thermal properties, dissolution characteristics and lithographic potential of a new poly(hydroxystyrene) derivative (PHS-EtOH) obtained by blocking the phenolic functionality with a saturated alcohol moiety through an ether linkage. The replacement of PHS with this modified polymer in a negative resist formulation has resulted in a dramatic improvement in dense line resolution.

The introduction of the hybrid sol-gel silica glass for direct semiconductor dielectric layer process involves three aspects of photolithography processes. First, the hybrid sol-gel silica glass is possible for the low k dielectric process. Second, it is also photosensitive and UV- patternable at 193 nm or shorter wavelength as the photoresists. Third, it can be used for direct dielectric process that can dramatically simplify the process flow and act as both dielectric materials and photoresist. To directly fabricate semiconductor dielectric layer by using spin-on and UV-patternable materials, to grow glass directly on the quartz, glass or even on the wafer substrate, to have photosensitive materials suitable for direct dielectric layer lithography process is in demand. With decreasing feature sizes, shorter wavelength for exposure is needed. At 193 nm wavelength, most of the materials are not transparent. Hybrid sol-gel silica glass in one of the UV- patternable materials for direct electronic device processing. It may be useful for reticle, DRAM, flat panel or even ASIC manufacturing. It can be 'formed' into intricate and precise 3D configuration. Exposure to DUV or 193 nm light result in a polymerization of the underlying sol-gel glass. the process alters the chemical properties within the bulk of the material as well as at the surface.

Typically, the Dill ABC parameters for optical resist are determined by coating a resist on a nonreflecting substrate and then measuring the change in the intensity of transmitted light at the wavelength of interest as a function of incident energy. Resists absorbance may not be selective in isolating and measuring only the photoactive species, and in some cases changes in absorbance can not be directly correlated to changes in the concentration of the photoactive species. FTIR spectroscopy can directly measure changes in the photoactive species by isolating and measuring absorbance peaks unique to the photoactive species by isolating and measuring absorbance peaks unique to the photoactive species. FTIR, employed in reflectance mode, is not constrained to transparent substrates, but can instead be used with silicon wafers or chrome coated quartz plates. The ability to use these substrates, but can instead be used with silicon wafers or chrome coated quartz plates. The ability to use these substrates is important when determining Dill's C parameter under e-beam exposure where the degree of back-scattered electrons is dependent on the underlying substrate, and the use of quartz is prohibited due to charging considerations. Dill's C parameter is determined for a variety of commercial i-line resist under both e-beam and i-line exposure. The ProABC software, a lithography simulator that extracts ABC parameters through a best fit of model to data, is employed to extract Dill's C parameter. This software has been specially modified to allow FTIR absorbance input.

We have surveyed the commercial resist market with the dual purpose of identifying diazoquinone/novolac based resist that have potential for use as e-beam mask making resists and baselining these resist for comparison against future mask making resist candidates. For completeness, such a survey would require that each resists be compared with an optimized developer and develop process. To accomplish this task in an acceptable time period we have chosen to perform e-beam lithography modeling to quickly identify the resist developer combinations that will lead to superior resists performance. We describe the development and verification of a method to quickly screen commercial i-line resists under e-beam exposure with different developers. This was accomplished by determining modeling parameters for i-line resist from e-beam exposures, modeling the resist performance, and comparing predicted performance versus actual performance. We evaluated whether the technique of combining e-beam resist modeling with lithography can be used to quickly and efficiently screen i-line resists for use in e-beam mask making. This was accomplished by comparing experimentally determined resists sensitivities and profiles with those predicted from ProBeam/3D lithography modeling software.

While positive photo resists make up the majority of the DUV market, negative resists have gained acceptance in IC manufacturing. Typically, negative photo resists can be used for a wide variety of feature types with minimal print bias including posts, lines/spaces and isolated lines. In some instances, negative resist are being investigated to print trenches and contact holes. Although negative resists are promising, there has been one issue. Dense line resolution has been limited by the onset of microbridging. Currently, minimum resolution for equal lines and spaces is about 200 nm with 0.26N developer, using conventional illumination. Recent developments in negative DUV resist technology have eliminated microbridging in 0.26N developer and has resulted in a significant increase in resolution. In addition to resolution and overall lithographic performance for sub 200 nm features, the PEB sensitivity, PED stability and other key resist performance capabilities will be demonstrated.

An exhaustive heat-transfer analysis of 200-mm and 300-mm bake equipment has been conducted to infer the temperature uniformity on the wafer from the time it is set on the plate until the end of the bake process. The objective of the analysis was to gain insight into the heat transport to the wafer and improve the thermal uniformity of the wafer. During the soft, hard and post-exposure bake processes, the temperatures to which the wafer is heated can range from 50 degrees to 250 degrees C. The influence of the variables that contribute to the temperature nonuniformity, namely the height of the proximity pins, wafer warp and bow, heater thickness, insulation of the bake plate, and lid material, have been analyzed. The analysis has been carried out using computational fluid dynamics packages, FLUENT/UNS and FIDAP. The accuracy of the numerical simulations has been verified through analytical solution is presented which provides a closed-form expression for the temperature of the wafer in terms of Biot number, a dimensionless parameter. The temperature rise of the wafer based on this simple expression compares very favorably with the detailed axisymmetric numerical solution that was carried out using variable material properties and the complex boundary conditions for the geometry of a 200-mm bake plate. The radial temperature variation on the wafer after 100 seconds on the bake plate also matches very well with the measurements. Based on the success of the modeling results with the 200-mm bake plates, a 300-mm bake plate analysis was conducted to determine if the temperature uniformity would be within specifications. The analysis revealed some key factors that caused temperature nonuniformity and the design was then altered to improve the temperature uniformity. Subsequent measurements confirmed the improvement of the temperature uniformity.

The first objective of this project was to characterize the lithographic performance of an advanced Acetal-based DUV resists. This resist is targeted for 0.25-0.18 micron geometries. The sensitivity of film thickness and uniformity to critical process parameters such as final dry spin time in the coater, soft bake time, soft bake temperature, method of soft bake, exhaust and vacuum levels in the soft bake were investigated. The second objective was to compare the material and lithographic performance properties of the advanced Acetal-based DUV resist, an advanced ESCAP-based DUV resists, and a third generation i-line resist. An advanced SVG track system that was clustered with an advanced Micrascan was used in these experiments. This lithography cluster tool represents a typical high volume production tool for device features of 0.25-micron and below.

The need for antireflective layers for good lithographic performance is a necessity for 193 nm wavelength exposures. In this paper we will illustrate two solutions for reflectivity control. The first is a spin-on organic bottom antireflectivity coating optimized for 193nm resist and the other is an inorganic film, SiOxNy.

In the semiconductor industry, structures down to 100 nm may be created by conventional mask lithography. To overcome this technological barrier, new tools have to be developed. Although electron-beam lithography can generate structures in this geometrical dimension, its disadvantages complicate a routine use. Scanning probe microscopies, on the other hand, are promising tools for the fabrication of nanometer sizes structures which are independent of these constraints. Several applications of scanning probe microscopes to nanolithography are reported. Their main disadvantages are their limitation to specific substrates like Silicon or Titanium, special resist like monolayer inorganic materials or low resist thicknesses not suitable for industrial use. We present a scanning probe technique which is able to create positive and negative structures on a conventional electron beam resist in development liquid. The tip of the scanning probe microscope is scanned in direct contact to the resist surface under a defined load force. With this technique we were able to create arbitrary 3D structures with widths between 80 nm and 80 micrometers and depths between 5 nm and 0.5 micrometers in e-beam resists. The main advantage of the presented technique is the fabrication of oblique structures in one step which cannot be done by any other lithography technique.

The effect of an alkali decomposable additive on a chemically amplified (CA) positive electron-beam (EB) resists was studied. HalogenoMethylEster (HME), 1,4- bis(bromoacetoxy) benzene was synthesize and used as an alkali decomposable additive. The hydrophobic HME decomposed with an alkali solution and changed into a hydrophilic, which in turn increased the alkali dissolution rate of the exposed region of the resist and enhanced the resist contrast. In addition, the bromomethyl groups and ester groups are hydrolyzed with a high degree of polarity change. HME having the large dissolution acceleration effect at an exposed region is suitable for application as a positive resist. HME was added to 2-component CA positive EB resist consisting of a base polymer and a photoacid generator. As a result of a high degree of polarity change, HME enhanced the resist contrast with no loss in sensitivity. The delineation of a fine 0.13 micrometers hole-pattern was possible with the addition of HME. The addition of HME rendered the sidewalls smooth and vertical.

An improved single layer lithographic metal lift off process which relies on formation of an inhibition layer at the top of the resist film by a simple treatment with an aqueous TMAH solution is introduced. The improvements that lead to an increase in the amount of overhang in the process are a flood exposure step prior to the post exposure bake and the use of a solvent containing TMAH solution of the soak. Both improvements can be used to enhance the amount of overhand above the defined space to arrive at desirable result for a single layer metal lift-off process. A basic chemical mechanism responsible for the formation of the overhang is proposed. The new lithographic processes described are capable of providing resist patterns with resolution better than 0.5 micrometers isolated spaces with a 0.54 NA i-line stepper in a facile single layer process.

A combination of methods has been applied to determine the glass transition and decomposition temperatures for several series of methacrylic copolymers used in commercial 193 nm resist as a function of the environment experienced by the protective group. The decomposition of the MAdMa and MLMA monomers which are the basis of the commercial AZ EXP AX- 1000P system is not appreciably catalyzed by the presence of MAA comonomers, leading to the conclusions that there is no autocatalytic effect in the deprotection of photoresists using these groups. AZ EXP AX1000P is found to have a high Tg of about 154 degrees C, which is corroborated by thermal flow measurements of developed resist features. Due to a decomposition process initiated by one of the other resist components, the formulation is presently not of the annealing type.

In the experiment, various ion species are implanted to the developed images to improve etching and thermal flow resistance of Deep UV chemically amplified resists. Among various ion species, it is found that Argon ion did not affect the photoresist thickness and critical dimension after ion implantation. Much improved results could be obtained. Untreated contact hole patterns start flowing on 120 degrees C and finally are filled up on 130 degrees C with noticeable film shrinkage. On the other hand, Argon implanted contact hole patterns are standing still up to 170 degrees C without any thickness shrinkage and CD variation. Application of higher temperature results in the protrusions at the bottom of the resist profiles. Pattern deformation after dry etching process can be prevented. Cross-sectional SEM micrographs of the ion implanted contact hole patterns show clear interface between the hardened and the unhardened. SIMS analysis of the ion implanted photoresists reveal the presence of the ions at the surface of the substrate, not in the resist. Detailed mechanistic study will be discussed. Application of this process to bilayer resist process and a new antireflective layer has been tried and evaluated. And also the effects of accelerating energy and ion dose on reflective index of carbonized layer have been investigated. RI analysis shows the change of n and k value according to energy and ion dose. It can be speculated that the transparent matrix resin changed to highly absorbing amorphous carbon based materials. It is quite sure for that the n and k value can be controlled for the application of bottom antireflective layer. This new ARC material is very compatible to resist and est to strip, compared to conventional Organic Bottom ARC material. Thickness optimization for the ARC, application to real device and etching characteristics are under development in our lab.

New photoresists and processes are required for sub 0.15 micrometers design rules and currently an important effort is on- going for single layer resists optimization at 193 nm. Top surface imaging can be an interesting alternative approach. An all dry chemical vapor deposition (CVD) process based on plasma polymerized methylsilane (PPMS) or plasma polymerized dimethylsilane (PP2MS) provides a thin conformal and photosensitive layer at 193 nm. A thin amorphous film of Si- Si bonded material is deposited using plasma enhanced chemical vapor deposition with methylsilane or dimethylsilane as the gas precursor. Upon 193 nm exposure under air, photo-induced oxidation of the CVD resist occurs, generating a latent image. The image is then developed in a chlorine-based plasma, providing a negative tone process. This mask can be used to pattern a thick organic underlayer to provide a general bilevel process. Lithographic results on both a 193 microstepper as well as a full field production stepper are presented: resolution down to 0.10 micrometers equal L/S was obtained. A preliminary comparison between PPMS and PP2MS materials is presented, including FTIR results, stability of the films in air and lithographic performance including line edge roughness.

We present an investigation to study the degradation of PMMA, poly(methyl methacrylate), and ARP-610, poly(methyl methacrylate-co-methacrylic acid), during e-beam and DUV exposure. The change in the chemical structure of the polymer materials were analyzed using UV, IR, NMR spectroscopy, gel permeation chromatography and GC-MS. The formation of anhydrides within the isotactic parts of the co-polymer causes a bimodel and multimodal distribution of the fragments and, therefore, a more efficient dissolution process.

The design of photoresists for 193 nm exposure systems has received extensive attention, with variable lithograph processes based on single layer resist as well as bi-layer and top surface imaging resists already been developed. Single layer resist systems can generally be divided into two classes: alicyclic and acrylic based on the polymer backbone. In acrylic systems, etching resistance is achieved by attaching pendant groups that have low Ohnishi numbers. In alicyclic systems, the high etching resistant substituent is directly incorporated in the backbone. Excellent ArF single layer photoresists have been derived form both types of polymers in several investigations. This work report on terpolymers of maleic anhydride, t-butyl-5-norbornene-2- carboxylate and polycyclic methacrylate derivatives as a resin for ArF photoresists formulated. Using these terpolymers which have a compatible property for 2.38 wt percent TMAH developer. The effects of terpolymers, type of PAG, dissolution inhibitors, base component, baking temperature and time delay on ArF SLR are also investigated.

In order to develop a new series of chemically amplified photoresists for 193-nm lithography, norbornene substituted with a steroid derivative was copolymerized with maleic anhydride by free radical polymerization. The resulting polymers have excellent transmittance at 193 nm and possess good thermal stability up to 260 degrees C. The resist formulated with the polymers showed better dry-etching resistance than the conventional poly(hydroxystyrene) resist for Cl₂/O₂ plasma. With the standard developer, the resists from 0.15-0.20 micrometers patterns at doses of 5-18 mJ/cm² using an ArF excimer laser stepper.