In this paper, we calculated the numeric results of diffraction field in space of X-ray (λ=4.5nm) Fresnel zone plate based
on angular spectrum method, analyzed the axial and radial distribution patterns of X-ray Fresnel zone plate. The Full
Width at Half-Maximum (FWHM), Depth Of Focus (DOF) and Strehl efficiency of focus spot were studied. Discussed
the relationships between FPZ's design parameter and focus spot properties. At the condition of λ=4.5nm and the
outmost width Wn=50nm, the size of focus spot is proportional to the outmost width, and increase slowly with the
increase of number of zones and focus length; the DOF of focus spot increase at first; when the focus length increased to
40µm, the DOF incline to a constant; the focus spot's Strehl efficiency increased slowly with the increase of number of
zones and focus length.
X-ray transmission gratings (TG) have attracted much interest because of its wide use in x-ray
telescope, synchrotron radiation facilities, and target diagnostic in inertial confinement fusion, etc. In
this work, a 200 nm period master TG to diffract x-ray in the energy range 0.1-8keV has been
successfully fabricated by electron beam lithography followed by gold electroplating. In fabrication
processes, 500 nm resist was exposed by focused electron beam on polyimide free-standing-membrane
coated with a Cr/Au plating base. According to numerical simulation, the proximity effect due to
electron back-scattering from the substrate can be sharply reduced because of the thin polyimide
free-standing membrane substrates. PMMA resist was chosen due to its high resolution and good
performance in subsequent processes. After delicate dose test and shape modification of the proximity
effect caused by electron front-scattering, resist grating bars with 95 nm width and 200 nm period were
achieved. Subsequently, resist patterns were transferred to gold layer by electroplating. In future work,
with this master mask of TG, thousands of TG to diffract x-ray can be sufficiently replicated using
x-ray lithography.
A novel diffractive optical element (DOE), quantu-dot-array diffraction grating(QDADG), used in soft X-ray
spectroscopy has been fabricated for the first time. The QDADG, which consists of a large number of quantum dots
distributed on a substrate as sinusoidal function, has many advantages in theory over conventional transmission grating
(TG) in soft X-ray spectroscopy, such as doubtless diffraction efficiency, no higher-order diffraction and no
subordination diffraction maximum, and so on. So, it can be predicted theoretically to improve the precision and Signal
Noise Ratio of soft X-ray spectroscopy in laser plasma diagnosis. But, there are many difficulties in the fabrication of
soft X-ray spectroscopy QDADG because of its much small dimension and complex pattern. In this paper, a combined
lithography was proposed to fabricate QDADG including electron beam lithograph (EBL) and proximity X-ray
lithograph(XRL). The diffraction property of QDADG has also been proved to be consistent with theoretical prediction
from test experiment. In the process of fabrication, because of the thin film substrate of soft X-ray QDADG, the
backscattering of incidence electrons can be effectively restrained in the electron beam lithograph, which can cause
much higher resolution. Without proximity effect correction, QDADG with 250nm minimal unit has been successfully
fabricated. In order to further increase the spectroscopy resolution and dispersion power of QDADG, it is necessary to
carry out proximity effect correction in electron beam lithograph.
The combination of electron beam lithography (EBL) and x-ray lithography (XRL) has been developed to successfully fabricate x-ray transmittive diffractive optical elements (DOE) such as Fresnel zone plates (FZP) and transmittive gratings (TG). In fabrication processes, the master masks of FZP and TG were patterned with high resolution on free standing membranes by EBL and followed by electroplating. Subsequently, the final gold FZP and TG with vertical cross section were efficiently and economically replicated by XRL and electroplating. By using this combined method, FZP based on silicon nitride (SiNx) free standing membrane was achieved with 150 nm width of outermost ring and 6.7 high aspect ratio, due to a novel sandwich resist structure. A series of TG master masks (2000 g/mm, 3333 g/mm, and 5000 g/mm) were fabricated by EBL. Furthermore, final gold TGs with 2000 g/mm and 3333 g/mm were replicated by XRL. The spectrum of 2000 g/mm TG has shown its perfect performance in x-ray spectroscopy.
We introduce a combined e-beam and x-ray lithographic method to fabricate microzone plates (MZP) on free-standing silicon nitride films. An automatic design program is developed to draw the complex layout of MZP with very smooth boundaries. A gold MZP master mask with a minimum ring width of 250 nm is fabricated by e-beam lithography. The master mask is replicated using x-ray lithography (XRL) and nickel electroplating to obtain the final MZP. The combined lithographic technique produces a MZP with a pattern aspect ratio of 4.4:1.
In this paper, Beam Propagation Method (BPM) with Fast Fourier Transforms(FFT) is employed to efficiently calculate the diffract image in the wafer plane for both conventional and second generation synchrotron-based proximity x-ray lithography(PXL). In the simulation, a dark-field isolated space pattern silicon nitride/Ta x-ray mask is used for conventional PXL and a diamond /Ta x-ray mask is used for second generation PXL, the diffract image’s dependency on absorber thickness, mask-wafer gap, effective total blur, linewidth and absorber sidewall slope has been numerically evaluated. For conventional PXL, in order to obtain a isolated trench resolution of 50nm, the mask-wafer gap should be controlled below 5 micron, the optimization condition is mask-wafer gap 5 micron, Ta absorber thickness 300nm, effective total blur 10nm, absorber sidewall slope 3°, the corresponding aerial image contrast is 0.457; For second generation, in order to obtain a isolated trench resolution of 50nm, the mask-wafer gap can be as large as 10 micron. In order to obtain a isolated trench resolution of 35nm, mask-wafer gap should be controlled below 5 micron.
The Micro-processing & Nano-technology Laboratory at the Institute of Microelectronics, Chinese Academy of Sciences (CAS), is equipped with a GCA 3600F PG&3696, a JBX 6AII & JBX 5000LS EB, and an ETEC MEBES 4700S EB. For a long time we have been engaged in the research and manufacture on Optical Resolution Enhancement Technology (RET) and E-Beam Direct Writing Technology. In this paper the following technologies will be described: PSM, OPC EBDW,EPC,Match & Mixed Lithography technology. Through the application of RET in optical lithography system, we completed the 0.2 um pattern with the g line and I line light source, which is the necessary preparation for 100nm node with 193nm light source. By means of match & mixed lithography and nanofabrication technology, 20nm-50nm gate CMOS transistor and 100nm gate HEMT are successfully developed.
T-shaped gate formation is a important process step in the fabrication of high frequency monolithic microwave integrated circuits (MMIC), many different lithography process have been used for this purpose, such as bi-layer or tri-layer using e-beam lithography, hybrid UV-e-beam lithography. Proximity x-ray lithography (PXL) has shown many advantages in the MMIC manufacturing, such as high resolution, large process windows, low cost and high throughout, and so on. In this article, a new ZEP520/P(MMA-MAA)/ZEP520 tri-layer process using synchrotron-based PXL is proposed for the T-shaped gate formation, without any additional intermediate layer, the resists intermixing problem has been solved successfully, a dark-field isolated trench x-ray mask was used for this purpose. A three stage development process using xylene for the head, MIBK:IPA=1:3 for the middle and xylene for the foot was also used. Initial work has shown this process to be robust.
Some research results in advanced optical lithography, Electron beam lithography, X-ray lithography are introduced in this paper. For advanced optical lithography, optical proximity correction and phase-shift masking (PSM) are studied, and 150nm pattern is achieved by i-line Stepper using transparent PSM. For e-beam lithography, the resist process, proximity effect correction and mix & match technologies are investigated, and 27nm CMOS device is successfully fabricated. The 0.15μm GaAs PHEMT devices are successfully fabricated by employing X-ray lithography.
The use of Alternating phase-shifting mask has been demonstrated to be a most powerful approach to expand resolution limitation and expand the process window of lithography. But the phase conflict problem limits the application of alt-PSM. For dark field alt-PSM, node connection PSM is a feasible method to solve the problem. We investigate the application of this method at 100nm node by simulation with ArF light source. The results prove that alt-PSM with conventional partial coherence illumination can be applied in the manufacturing of random interconnect layer. This method can expand the process window effectively. The program that can achieve the pattern decomposition automatically is also developed. We’re sure that combined with optical proximity effect correction, this multi-exposure technology can fulfill the need of 0.1-μm generation logic IC lithography.
The process of resist is of great importance to the resolution of e-beam direct-writing exposure. ZEP520 is an excellent positive e-beam resist, which has high resolution, high sensitivity, high contrast as well as good dry etch resistance. In this paper, the e-beam exposure process of ZEP520 on Si and GaAs substrates and its application in nanoelectrode-pair and single-electron transistor have been studied. On Si substrate, the contrast, sensitivity and resolution of ZEP520 have been investigated in detail, and the influence of exposure dose and resist thickness on the size of ZEP520 patterns has been discussed. The contrast of 425nm-thick ZEP520 on Si is 2.70. The sensitivity of ZEP520 is <5 μC/cm2. The size of ZEP520 lines and circular holes decreases with exposure dose decreasing and thickness increasing. 70 nm wide lines and 110-nm-diameter dots can be exposed on Si substrate using 110 nm thick ZEP520. The flaws of ZEP520 on GaAs can be eliminated by fore-baking the GaAs substrate; and 130 nm wide lines can be exposed on GaAs using ZEP520. In regard to application, a nanoelectrode-pair with a 60 nm space has been fabricated using ZEP520. And a kind of in-plane singe-electron transistor (SET) has also been fabricated on silicon-on-insulator (SOI) substrate, which has a 110 nm wide Si Coulomb island and shows Clear Coulomb staircases in Ids from the Ids-Vds characteristics and differential conductance (dIds/dVds) oscillations from the dIds/dVds-Vds characteristics at 2 K.
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