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Recent work in electron cyclotron resonance chemical vapor deposition (ECR‐CVD) SiC coating technology has demonstrated the potential for fabricating high‐quality SiC membranes for x‐ray lithography masks. Stoichiometric SiC coatings were deposited on 100‐mm‐diam silicon wafers at a susceptor temperature of 930 °C in a single‐wafer ECR‐CVD system at deposition rates of 200 Å/min with better than ±5% thickness uniformity and ±1% wafer‐to‐wafer reproducibility. The coatings were deposited under tensile stress, with a wafer‐to‐wafer stress repeatability of ±15%. The coatings were extremely smooth, and x‐ray diffraction (XRD) and transmission electron microscopy (TEM) studies showed that they were amorphous with scattered submicron crystalline inclusions. One‐ and 2‐μm‐thick membranes were made in 30 and 50 mm diameters at yields of 80%. A peak transmittance of 65% was measured at 633 nm for 1‐μm‐thick SiC membranes. The bi‐axial elastic modulus, E/(1-ν), of the SiC membranes was (4–6)×1012 dyn/cm2, about three times greater than that of (100) Si membranes. Hydrogen was undetectable in the form of either CH or SiH bonds to within the experimental detection limit of ≪10 ppm. Out‐of‐plane distortion could not be detected after an absorbed dose of 9.6 or 29 MJ/cm3 during exposure at the Center for X‐ray Lithography beamline at the University of Wisconsin’s Aladdin synchrotron. The membrane transmittance decreased by about 1% after the 29 MJ/cm3 dose. Plans for future work include modifications to the ECR‐CVD equipment to increase substrate temperature uniformity, temperature limit, and deposition rate, and to reduce defect density.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures (Volume:9 , Issue: 6 )
Date of Publication: Nov 1991