6 December 2004 FEP-171 resist thickness optimization and dry etch screening on NTAR7 chrome substrates for Sigma7300 DUV laser pattern generator
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Chrome and resist thickness are limiting factors for final resolution on mask. The trend in mask manufacturing is consequently moving towards thinner chrome and resist films. The Sigma7300 is a 248nm DUV laser pattern generator with optical resolution approaching 100nm. The earlier standard mask blank for the mask writer had 1030Å thick AR8 chrome together with 4000Å FEP-171 resist. To fully benefit from the resolution capability of the mask writer, this study aimed to investigate the 730Å thick NTAR7 chrome together with thinner FEP-171 resist. The dry etch characteristics of thin chrome and thin resist were also studied. As a first step, a set of plates with varying resist thickness was exposed to extract the swing curve. The resist thickness ranged from 3050Å - 3600Å in steps of 50Å. The fitted curve based on the dose required to break through the resist (dose-to-clear) for different thicknesses showed a maximum at approximately 3200Å. A resolution improvement of about 10nm was achieved in this resist thickness compared to the earlier 4000Å film. Design of Experiments (DoE) was used to perform a screening of the dry etch process on NTAR7 and the 3200Å resist. All plates were exposed using the Sigma7300. Etching was performed on a UNAXIS Gen III Mask Etcher with standard Cl2/O2/He gas mixture. The dry etch process developed from the DoE responses was used to characterize the lithographic performance on mask from the Sigma7300 together with the new optimized blanks. CD linearity <10nm (range) was demonstrated both for clear and dark isolated lines down to 180nm line width. Global CD uniformity <6nm (3s) was achieved and very well defined chrome profiles for 150nm isolated clear lines and 130 nm isolated dark lines were demonstrated.
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Johan O. Karlsson, Johan O. Karlsson, Kezhao Xing, Kezhao Xing, Adisa Bajramovic, Adisa Bajramovic, Henrik Dahlberg, Henrik Dahlberg, Charles Bjornberg, Charles Bjornberg, Peter Hogfeldt, Peter Hogfeldt, Lars Kjellberg, Lars Kjellberg, Hans Fosshaug, Hans Fosshaug, Anna Dahlberg, Anna Dahlberg, Axel Lundvall, Axel Lundvall, } "FEP-171 resist thickness optimization and dry etch screening on NTAR7 chrome substrates for Sigma7300 DUV laser pattern generator", Proc. SPIE 5567, 24th Annual BACUS Symposium on Photomask Technology, (6 December 2004); doi: 10.1117/12.569653; https://doi.org/10.1117/12.569653

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