Directed self-assembly (DSA) is one of the candidates for next generation lithography. Over the past years, many papers and presentation have been reported regarding DSA, and Tokyo Electron Limited (TEL is a registered trademark or a trademark of Tokyo Electron Limited in Japan and /or other countries.) also has presented the evaluation results and the advantages of each1-10. Polystyrene-b-polymethyl methacrylate (PS-b-PMMA) has been used in many report because the polymerization technology is established and it is easy to form vertical patterns. In addition, the chemical epitaxy flow for PS-b-PMMA has established well to improve defectivity, line edge roughness and line width roughness. On the other hand, it is difficult to achieve less than 24nm pitch pattern by PS-b-PMMA because of the low chi parameter. In this paper, the combination process of DSA and SADP (self-aligned double pattern) is proposed for further small pitch pattern by PS-b- PMMA and latest results are reported.
Direct Self-Assembly (DSA) is expected to be applied to patterns below 20 nm, and many applications have been proposed along with several lithography techniques. The advantage of DSA is that the molecular weight of the polymer can control the pattern size and achieve a fixed pattern pitch. On the other hand, the DSA process faces the technical challenges of pattern defects, line edge roughness (LER), and pattern transfer to the underlying layer. Tokyo Electron has reported the results of these improvements in the past SPIE. This report introduces each optimization method and shows you the next steps.
Directed self-assembly (DSA) is one of the candidates for next generation lithography. Over the past years, many papers and presentation have been reported regarding DSA, and Tokyo Electron Limited (TEL is a registered trademark or a trademark of Tokyo Electron Limited in Japan and /or other countries.) also has presented the evaluation results and the advantages of each1-9. Especially, the chemo-epitaxy process has advantages for the sub 20nm line & space patterns to apply to active area patterns for DRAM, fin patterns for Logic and narrow pitch of metal patterns. One of the biggest advantages of DSA lines is that the pattern pitch is decided by the specific factors of the block copolymer, and it achieves the small pitch walking as a consequence. In this paper, the latest results regarding the defect reduction work regarding chemo-epitaxy line & space pattern is reported. And, sub-10nm process flow without using high-chi BCP is discussed.
Directed self-assembly (DSA) is one of the candidates for next generation lithography. Over the past years, many papers and presentation have been reported regarding DSA, and Tokyo Electron Limited (TEL is a registered trademark or a trademark of Tokyo Electron Limited in Japan and /or other countries.) also has presented the evaluation results and the advantages of each 1-8. Especially, the chemo-epitaxy process has advantages for the sub 20nm line and space patterns to apply to active area patterns for DRAM, fin patterns for Logic and narrow pitch of metal patterns. One of the biggest advantages of DSA lines is that the pattern pitch is decided by the specific factors of the block copolymer, and it achieves the small pitch walking as a consequence. On the other hand, the chemo-epitaxy process can be applied to the hexagonal close-packed arrangement holes 8. Those holes are expected to be the patterns for DRAM storage. In this paper, the latest results regarding the defect reduction work regarding chemo-epitaxy line and space pattern is reported. Especially, the defect density of the patterns that were transferred to spin on carbon (SOC) film is confirmed.
Directed self-assembly (DSA) is one of the candidates for next generation lithography. Over the past years, many papers and presentation have been reported regarding DSA, and Tokyo Electron Limited (TEL is a registered trademark or a trademark of Tokyo Electron Limited in Japan and /or other countries.) also has presented the evaluation results and the advantages of each1-6. Especially, the chemo-epitaxy process has advantages for the sub 20nm line & space patterns to apply to DRAM active area, Logic fin and narrow metal patterns. One of the biggest advantages of DSA lines is that the pattern pitch is decided by the specific factors of the block copolymer, and it achieves the small pitch walking as a consequence. On the other hand, the chemo-epitaxy process can be applied to the hexagonal close-packed arrangement holes6. Those holes are expected to be the patterns for DRAM storage.
In this report, we present the latest results regarding the defect reduction and LER improvement work regarding chemoepitaxy line & space pattern. In addition, we update the evaluation results regarding chemo-epitaxy hole pattern.
Directed self-assembly (DSA) has been investigated over the past few years as the candidate for next generation lithography. Especially, sub 20nm line and space patterns obtained by chemo-epitaxy process are expected to apply to DRAM active area, Logic fin and narrow metal patterns. One of the biggest advantages of DSA lines is that the pattern pitch is decided by the specific factors of the block copolymer, and it indeed the small pitch walking as a consequence. However, the generating mechanism of the DSA pattern defect is still not cleared1-4 and the line edge roughness (LER) is not overtaken self- aligned quadruple patterning (SAQP).
In this report, we present the latest results regarding the defect reduction and LER improvement work regarding chemoepitaxy line and space pattern. In addition, we introduce the result of application of chemical epitaxy process to hole pattern.
Placement of cylinders in hole multiplication patterns for directed self-assembly is the topic of this computational study. A hole doublet process applying a corner rounded rectangle guide is the focus of this work. Placements including morphology fluctuation can be analyzed by dissipative particle dynamics simulation. When the surface of guides and underlayers are modified from strong polymethyl methacrylate (PMMA) attractive to weak PMMA attractive, two PMMA cylinders can be contacted at the underlayer. Even when the PMMA domain had a separated morphology, hole placement errors (HPE) were similar to those with connected domains which occurred in the strong PMMA affine case. In general, HPE in longitudinal guide direction was larger than in the shorter direction. It is interesting to note that HPE in the longer direction was decreased by increasing the guide size in shorter direction. Cylinder tops likely fluctuate; cylinder middles may fluctuate as well in some cases. Means for HPE reduction were also tested computationally: reducing the guide thickness and employing dimpled structures. Decreasing guide thickness was effective for reducing HPE; however, guide thicknesses that were too thin prevented PMMA domains from forming vertical cylinders. Dimpled structures also reduced HPE. The depth of the dimple had a little influence on the distance of two holes when the guide structure was fitted with hexagonal packing for the block co-polymers.
Directed self-assembly (DSA) is one of the candidates for next generation lithography. Over the past few years, cylindrical and lamellar structures dictated by the block co-polymer (BCP) composition have been investigated for use in patterning contact holes or lines, and, Tokyo Electron Limited (TEL is a registered trademark or a trademark of Tokyo Electron Limited in Japan and /or other countries.) has presented the evaluation results and the advantages of each-1-5. In this report, we will present the latest results regarding the defect reduction work on a model line/space system. Especially it is suggested that the defectivity of the neutral layer has a large impact on the defectivity of the DSA patterns. Also, LER/LWR reduction results will be presented with a focus on the improvements made during the etch transferring the DSA patterns into the underlayer.
This manuscript shows the relationship between defectivity of a typical chemo-epitaxy sequence and the DSA-specific materials, namely the mat, the brush and the block co-polymer. We demonstrate that the density of assembly defects in a line-space DSA flow, namely the dislocations and 1-period bridges have a direct correlation to certain parameters in the synthesis sequence of these materials. The primary focus of this manuscript is on identifying, controlling and reproducing the defects-critical parameters in the block co-polymer synthesis process for a stable and low defect performance of DSA flows.
Directed Self-Assembly (DSA) is being extensively evaluated for application in semiconductor process integration.1-7 Since 2011, the number of publications on DSA at SPIE has exploded from roughly 26 to well over 80, indicating the groundswell of interest in the technology. Driving this interest are a number of attractive aspects of DSA including the ability to form both line/space and hole patterns at dimensions below 15 nm, the ability to achieve pitch multiplication to extend optical lithography, and the relatively low cost of the processes when compared with EUV or multiple patterning options.
Tokyo Electron Limited has focused its efforts in scaling many laboratory demonstrations to 300 mm wafers. Additionally, we have recognized that the use of DSA requires specific design considerations to create robust layouts. To this end, we have discussed the development of a DSA ecosystem that will make DSA a viable technology for our industry, and we have partnered with numerous companies to aid in the development of the ecosystem. This presentation will focus on our continuing role in developing the equipment required for DSA implementation specifically discussing defectivity reduction on flows for making line-space and hole patterns, etch transfer of DSA patterns into substrates of interest, and integration of DSA processes into larger patterning schemes.
We report computational study for directed self-assembly (DSA) on morphologies’ dislocation caused by block copolymers’ (BCPs’) thermal fluctuation in grapho-epitaxial cylindrical guides. The dislocation factor expressed as DSA-oriented placement errors (DSA-PEs) was numerically evaluated by historical data acquisition utilizing dissipative particle dynamics simulation. Calculated DSA-PEs was compared with experimental results on two kinds of guide pattern, resist guide with no surface modifications (REF guide) and resist guide with polystyrene coated (PS-brush guide). Vertical distribution of DSA-PEs within the cylindrical guides was calculated and relatively high DSA-PEs near top region was deduced particularly in REF guide. The tendency of experimental DSA-PEs was well explained by the calculation including a fluctuation parameter on the wall particles. In PS-brush guide, calculated DSA-PEs was drastically increased with becoming the guide more fluctuating. This result indicates to fabricate hard and steady guide condition in PS-brush guide so as to achieve better placements. From the variety of guide critical dimension (CD) computation, it is suggested that smaller guide CD is better to obtain good placements. The smallest DSA-PE value in this study was observed in PS-brush guide with smaller guide CD because of the strong restriction of BCP arrangement flexibility.
Grapho-epitaxy based hole shrink process of Directed Self-assembly (DSA) is one of the candidates for less than 30 nm hole pattern fabrication. The guide patterns of grapho-epitaxy are made by using ArF immersion scanner under the condition of near resolution limit to the 193-nm exposure. Hence, guide patterns have measurable level of edge roughness and edge placement errors. Those errors cause serious size errors and placement errors of DSA hole patterns. RED (Robust Edge Detection) is a new measurement function of CD-SEM for qualifying guide pattern shapes and DSA pattern shapes simultaneously. We also propose GBM (Grid Based Metrology) for the measurement of DSA hole's absolute placement error. In this paper, we applied the two methods for qualifying about 20 nm-node’s different polymer film thickness of DSA hole process. The DSA placement error from GBM result and relative DSA placement error obtained by RED are almost same as about 3nm (3sigma). This indicates both RED and GBM methods are correct to measure the DSA process error.
Next-generation lithography technology is required to meet the needs of advanced design nodes. Directed Self Assembly (DSA) is gaining momentum as an alternative or complementary technology to EUV lithography. We investigate defectivity on a 2xnm patterning of contacts for 25nm or less contact hole assembly by grapho epitaxy DSA technology with guide patterns printed using immersion ArF negative tone development. This paper discusses the development of an analysis methodology for DSA with optical wafer inspection, based on defect source identification, sampling and filtering methods supporting process development efficiency of DSA processes and tools.
Proc. SPIE. 9049, Alternative Lithographic Technologies VI
KEYWORDS: Lithography, Polymethylmethacrylate, Particles, 3D modeling, Scanning electron microscopy, Monte Carlo methods, Photomasks, Directed self assembly, Picosecond phenomena, Scanning transmission electron microscopy
In this report, morphology of cylinders by block copolymer (BCP) in the corner rounded rectangle guide patterns is
analyzed by simulation and compared with experimental results. In the case of the hole-multiplication, selection the
guide pattern size and the affinity of wall and under layer is necessary for stable micro structure. To search the good
guide conditions, Ohta-Kawasaki (OK) model and dissipative particle dynamics (DPD) are used. OK model is well
known as low cost simulation method, therefore it is expected to use for searching the good guide area roughly from
wide range. DPD is one of the strong candidates for DSA simulation, and it is used for prediction of the micro structure.
As results, the guide size area which has two PMMA cylinders by 2D OK model seems consistent with experimental
results, 3D micro structure by OK model and DPD are comparable, 3D simulations have good agreements with
experimental results observed by CD-SEM and STEM. Especially two cylinders connected each other at some point
predicted by 3D simulation is observed actually. These simulation approaches will be important to decide the lithography
mask design, film stack and pre-treatment conditions for more complex multiplication process, for example, the cut mask
Directed Self-Assembly (DSA) is one of the most promising technologies for scaling feature sizes to 16 nm and below.
Both line/space and hole patterns can be created with various block copolymer morphologies, and these materials allow
for molecular-level control of the feature shapes—exactly the characteristics that are required for creating high fidelity
lithographic patterns. Over the past five years, the industry has been addressing the technical challenges of maturing this
technology by addressing concerns such as pattern defectivity, materials specifications, design layout, and tool
requirements. Though the learning curve has been steep, DSA has made significant progress toward implementation
in high-volume manufacturing.
Tokyo Electron has been focused on the best methods of achieving high-fidelity patterns using DSA processing. Unlike
other technologies where optics and photons drive the formation of patterns, DSA relies on surface interactions and
polymer thermodynamics to determine the final pattern shapes. These phenomena, in turn, are controlled by the
processing that occurs on clean-tracks, etchers, and cleaning systems, and so a host of new technology has been
developed to facilitate DSA. In this paper we will discuss the processes and hardware that are emerging as critical
enablers for DSA implementation, and we will also demonstrate the kinds of high fidelity patterns typical of mainstream
A contact hole shrink process using directed self-assembly lithography (DSAL) for sub-30 nm contact hole patterning is reported on. DSAL using graphoepitaxy and poly (styrene-block-methyl methacrylate) (PS-b -PMMA) a block copolymer (BCP) was demonstrated and characteristics of our process are spin-on-carbon prepattern and wet development. Feasibility of DSAL for semiconductor device manufacturing was investigated in terms of DSAL process window. Wet development process was optimized first; then critical dimension (CD) tolerance of prepattern was evaluated from three different aspects, which are DSA hole CD, contact edge roughness (CER), and hole open yield. Within 70+/−5 nm hole prepattern CD, 99.3% hole open yield was obtained and CD tolerance was 10 nm. Matching between polymer size and prepattern size is critical, because thick PS residual layer appears at the hole bottom when the prepattern holes are too small or too large and results in missing holes after pattern transfer. We verified the DSAL process on a 300-mm wafer at target prepattern CD and succeeded in patterning sub-30 nm holes on center, middle, and edge of wafer. Average prepattern CD of 72 nm could be shrunk uniformly to DSA hole pattern of 28.5 nm. By the DSAL process, CD uniformity was greatly improved from 7.6 to 1.4 nm, and CER was also improved from 3.9 to 0.73 nm. Those values represent typical DSAL rectification characteristics and are significant for semiconductor manufacturing. It is clearly demonstrated that the contact hole shrink using DSAL is a promising patterning method for next-generation lithography.
This paper discusses the defect density detection and analysis methodology using advanced optical wafer inspection capability to enable accelerated development of a DSA process/process tools and the required inspection capability to monitor such a process. The defectivity inspection methodologies are optimized for grapho epitaxy directed self-assembly (DSA) contact holes with 25 nm sizes. A defect test reticle with programmed defects on guide patterns is designed for improved optimization of defectivity monitoring. Using this reticle, resist guide holes with a variety of sizes and shapes are patterned using an ArF immersion scanner. The negative tone development (NTD) type thermally stable resist guide is used for DSA of a polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymer (BCP). Using a variety of defects intentionally made by changing guide pattern sizes, the detection rates of each specific defectivity type has been analyzed. It is found in this work that to maximize sensitivity, a two pass scan with bright field (BF) and dark field (DF) modes provides the best overall defect type coverage and sensitivity. The performance of the two pass scan with BF and DF modes is also revealed by defect analysis for baseline defectivity on a wafer processed with nominal process conditions.
Directed self-assembly (DSA) has the potential to extend scaling for both line/space and hole patterns. DSA has shown the capability for pitch reduction (multiplication), hole shrinks, CD self-healing as well as a pathway towards LWR and pattern collapse improvement [1-10]. TEL has developed a DSA development ecosystem (collaboration with customers, consortia, inspection vendors and material suppliers) to successfully demonstrate directed PS-PMMA DSA patterns using chemo-epitaxy (lift-off and etch guide) and grapho-epitaxy integrations on 300 mm wafers. New processes are being developed to simplify process integration, to reduce defects and to address design integration challenges with the long term goal of robust manufacturability. For hole DSA applications, a wet development process has been developed that enables traditional post-develop metrology through the high selectivity removal of PMMA cylindrical cores. For line/ space DSA applications, new track, cleans and etch processes have been developed to improve manufacturability. In collaboration with universities and consortia, fundamental process studies and simulations are used to drive process improvement and defect investigation. To extend DSA resolution beyond a PS-PMMA system, high chi materials and processes are also explored. In this paper, TEL’s latest process solutions for both hole and line/space DSA process integrations are presented.
We report morphology of cylinder of diblock copolymers (BCP), which consist of polymer A and B, in cylindrical prepattern
holes by dissipative particle dynamics simulation in order to predict optimal cylinder profile. Configuration of
cylinder which consists of polymer B changes along with change of affinity of underlayer and guide wall for BCP. In the case of underlayer, neutral to both the polymer species shows the most stable cylinder shape. When affinity converts to either polymer, cylinder shape gets distorted. In the case of intergrading guide wall condition from A wet to B wet for a certain hole CD, polymer B, that constitutes cylinder, gradually loosen and stack on the guide eventually. Moreover
cylinder forms again for B wet larger hole. Free energy for hole CD is also investigated and the profile shows A wet wall
and B wet wall are suitable for hole shrink in a narrow and wide range of hole CD, respectively. Because free energy of
A wet wall varies widely for hole CD change. In contrast, free energy of B wet wall exhibits no significant changes and
the profiles signify that cylinder shapes relatively stable in wider range than A wet wall.
A method for using wet development in a directed self-assembly lithography (DSAL) application is reported. For the typical diblock copolymer poly(styrene-block-methyl methacrylate) (PS-b-PMMA), the PMMA area is removed by an oxygen plasma. However, the oxygen plasma has poor selectivity for the PS portion of the block polymer and etches it simultaneously. As a result, the thickness of the residual PS pattern is thinner than desired and creates a challenge for subsequent pattern transfer. A wet development technique is discussed which offers higher selectivity between the PMMA and PS blocks in the assembled pattern. Specifically, a method using a low pressure mercury lamp and conventional tetramethylammonium hydroxide (TMAH, 2.38%) developer is proposed. Using this method, DSA pattern formation is completed in a single track having coating, baking, exposure, and development modules.
Directed self-assembly (DSA) has the potential to extend scaling for both line/space and hole patterns. DSA has shown
the capability for pitch reduction (multiplication), hole shrinks, CD self-healing as well as a pathway towards line edge
roughness (LER) and pattern collapse improvement [1-4]. The current challenges for industry adoption are materials
maturity, practical process integration, hardware capability, defect reduction and design integration. Tokyo Electron
(TEL) has created close collaborations with customers, consortia and material suppliers to address these challenges with
the long term goal of robust manufacturability.
This paper provides a wide range of DSA demonstrations to accommodate different device applications. In
collaboration with IMEC, directed line/space patterns at 12.5 and 14 nm HP are demonstrated with PS-b-PMMA
(poly(styrene-b-methylmethacrylate)) using both chemo and grapho-epitaxy process flows. Pre-pattern exposure
latitudes of >25% (max) have been demonstrated with 4X directed self-assembly on 300 mm wafers for both the lift off
and etch guide chemo-epitaxy process flows. Within TEL's Technology Development Center (TDC), directed selfassembly
processes have been applied to holes for both CD shrink and variation reduction. Using a PS-b-PMMA hole
shrink process, negative tone developed pre-pattern holes are reduced to below 30 nm with critical dimension uniformity
(CDU) of 0.9 nm (3s) and contact edge roughness (CER) of 0.8 nm. To generate higher resolution beyond a PS-b-PMMA system, a high chi material is used to demonstrate 9 nm HP line/ space post-etch patterns. In this paper, TEL presents process solutions for both line/space and hole DSA process integrations.
Proc. SPIE. 8323, Alternative Lithographic Technologies IV
KEYWORDS: Lithography, Polymethylmethacrylate, Deep ultraviolet, Scanning electron microscopy, Photoresist materials, Directed self assembly, Picosecond phenomena, Photomicroscopy, System on a chip, Photoresist developing
We report on a contact hole shrink process using directed self-assembly. A diblock copolymer, poly (styrene-blockmethyl
methacrylate) (PS-b-PMMA), is used to shrink contact holes. Contact hole guide patterns for graphoepitaxy are
formed by ArF photoresists. Cylindrical domains of PMMA is removed using organic solvents after DUV (λ <200 nm)
irradiation. In this work, it is found that a solvent system is the best developer from the evaluated single solvent systems
and mixed solvent systems. The wet development of PS-b-PMMA strongly depends on total exposure dose of DUV
irradiation. With lower exposure dose, the cylindrical domains of PMMA are not clearly removed. With optimum
exposure dose, PMMA is developed clearly. The contact hole guide patterns of 75 nm in diameter are successfully
shrunk to 20 nm in diameter using the wet development process.
We report wet development technique for directed self-assembly lithography pattern. For typical diblock copolymer,
poly (styrene-block-methyl methacrylate) (PS-b-PMMA), the PMMA area is removed by O2 plasma. However, O2 plasma attack also etches off PS area simultaneously. As a result, the thickness of residual PS pattern is thinner and it
causes degradation of PS mask performance. PS thickness loss in the device integration is not desirable as etching mask
role. In this work, we applied wet development technique which could be higher selectivity to keep PS film thickness
after pattern formation. Especially, we propose the method using low pressure mercury lamp and conventional TMAH
(2.38%) as developer. It is expected to accomplish pattern formation in one track with coating, baking, exposure and
In the photolithography process, with the miniaturization of pattern size, depth of focus (D.O.F) is also becoming smaller
and smaller. This indicates that the control of particles on the wafer backside which has not been regarded as a problem
so far is becoming important.
Therefore, we considered that wafer backside is cleaned just before a wafer is transferred into the exposure equipment in
order to prevent the occurrence of a Focus error and reduce the contamination of the exposure chuck.
As a result, it was verified that the cleaning of wafer backside at the memory production line of the 70nm node can
reduce the contamination of the exposure chuck and can extend the period of maintenance for the exposure equipment.
Moreover, it was also verified that the cleaning of wafer backside can improve productivity.
The lithography process on topographic substrate is one of the most critical issues for device manufacturing.
Topographic substrate-induced focus variation occurs between top position and bottom position in a layer. That is,
common depth of focus is reduced. This focus variation is sure to ruin the focus budget in low k1 lithography.
From the focus budget of CMOS device, substrate topography is required to be less than 30nm for hp 45-nm
generation devices and less than 15nm for hp 32-nm generation devices.
In this paper, the authors evaluate a novel concept for hp45-nm generation dual damascene layer for global surface
planarization. The novel concept is thin planarization layer with bottom anti-reflecting (BAR) function. This
planarization layer with optical performance is materialized by UV crosslink materials and process. This concept is
expected to lead to a simpler planarization process. Thin planarization layer with BAR function clear BARC layer and
simplifies the etching process.
Our study showed that the planarization performance of UV crosslink layer with 100nm thickness was 20nm
thickness bias between the field area and dense via hole area. This thickness bias achieved the requirement of hp
45nm generation. Furthermore, fine resist pattern was resolved on the planarization layer by the optimization of acid
components and additive.
It is vital to control Critical Dimension (CD) within a wafer and pattern profile in photolithography process. We have previously reported our evaluation results with chemically amplified resists that one of the causes of pattern profile fluctuation is a change in resist film composition before exposure such as non-uniform distributions of additives (photo-acid generator (PAG), quencher) concentration and casting solvent etc.; and thus resist film property control is essential to suppress these factors . This is also true for thin resist film in finer line process and with top surface imaging. In the same paper , we have reported that a straightforward method to understand a change in film property is to check the amount of thickness loss by developing unexposed film after post apply bake (PAB). This method can be applied to thin film as well. We created unexposed films with the thickness range of 50-900nm by changing the total solid content (TSC) in resist and spin speed at resist coating. The amount of thickness loss significantly increased with sub-200nm thickness; the film property of which was quite different from that of 200nm-or-over thickness. Moreover, pattern line edge roughness (LER) as well as pattern surface roughness was prominent with 100nm-thick film even when we used a resist which has an ability to create good patterns on film with a thickness of 400nm. This is because the film quality diminishes in bulk below a certain thickness, while the property on the surface or interface layer predominates. Then we studied Scan coating to control thin film property. In Spin coating, chemical liquid dispensed on static wafer is spread by spinning the wafer and solvent is evaporated to form a film. On the other hand, in Scan coating, wafer remains static even after chemical liquid is dispensed and the wafer is dried under reduced pressure -; which means the thinner evaporation rate is slower than that in Spin coating and film property control may be easier. We, therefore, expect that Scan coating is a possible method to control CD and pattern profile. In this study, we compared the process performance and film property of KrF resist films by Scan and Spin coatings and examined the film composition control.
The coating procedure of polymer solutions by the scanning technique is developed for LSI technologies at the next generation, where a polymer solution as resists and inter-layer dielectric films is coated on a flat substrate, and then only the solvent is vaporized and removed, and finally the thin film is remaining there. In case of applying to the photo-lithography process, scan coating and its drying processes work together for astonishing flatness in 1% fluctuation range. When the coated polymer solution is dried under reduced pressure or vacuum, the thickness distribution of the resultant film should be accurately prospected and controlled by parameters. The film thickness is generally thicker at the edge and thinner inside from there than the average thickness. A typical thickness profile of a resist film is shown in Figure 1 . The phenomena are always observed, but have not been analyzed numerically. In this paper, we report a numerical model of the drying process of liquid film including polymers and give the essential parameters to the coating and drying processes. The parameters are focused on a vaporization rate, diffusion coefficients, coated solution thickness and intrinsic viscosity, which were calculated by simplified dynamical models of Langmuir's vaporization rate equation and Einstein relation at complex polymer solutions.
In a photolithography process, it is vital to control Critical Dimension (CD) within wafer. In the current process, although parameters are controlled during post-exposure bake (PEB) and development, only film thickness is checked before exposure for the CD control. However, as the fine patterning by using chemically amplified resist (CAR) has progressed, CD control within wafer has been affected by very small changes of protecting groups; distribution of additives (PAG, quencher etc.) concentrations, and solvent concentrations, thus it has become more important to control film compositions = film properties before exposure. Following by CD variations within wafer caused by air flow in Post applied Bake (PAB) chamber, we examined evaluation methods of KrF resist film properties and made various evaluations of unexposed film after PAB. This paper describes correlation between CD and PAG, quencher, and solvent concentration; consideration of CD variations mechanism based on the correlation data; and problems when shifting to the next generation process.