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17 December 2003 Low-thermal-expansion material for EUV applications
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The Coefficient of Thermal Expansion (CTE) properties and surface finish values of a low expansion glass-ceramic material produced by Ohara called CLEARCERAM were measured and compared to the SEMI P37 EUVL specifications, which include dL/L profiles, CTE variation, surface roughness, and flatness. The results showed that CLEARCERAM-Z HS, a derivation from the conventional CLEARCERAM material, had the CTE (+19 to +25C) variation of 0±15 ppb/degree C in standard deviation with the intra block uniformity of Delta CTE = 3 ppb/degree C in the 40x40mm, which corresponds to the CTE specification of Class C in the SEMI standard P37 for Extreme Ultraviolet Lithography (EUVL) Photomask Substrates. Also polishing experiments targeting the surface specifications in SEMI P37 were performed. Surface flatness less than 100 nm (meeting Class A in SEMI P37) and surface roughness of 0.15 nm Rms (Conforming to the SEMI P37) were obtained and reviewed. The results of the CTE property and polished surface evaluations suggest that CLEARCERAM-Z HS is a suitable candidate material to meet SEMI standard P37 for EUVL Photomask Substrates, while further improvements of CTE measurement accuracy and polishing processes are necessary to fully meet the current specifications.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Kousuke Nakajima "Low-thermal-expansion material for EUV applications", Proc. SPIE 5256, 23rd Annual BACUS Symposium on Photomask Technology, (17 December 2003);

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