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Proceedings Paper

Finishing of EUV photomask substrates by CNC precessed bonnet polisher
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Paper Abstract

The progressive transition from Excimer to EUV lithography is driving a need for flatter and smoother photomasks. It is proving difficult to meet this next generation specification with the conventional chemical mechanical polishing technology commonly used for finishing photomasks. This paper reports on the application of sub-aperture CNC precessed bonnet polishing technology to the corrective finishing of photomask substrates for EUV lithography. Fullfactorial analysis was used to identify process parameters capable of delivering 0.5 nm rms surface roughness whilst achieving removal rates above 0.1 mm3/min. Experimental results show that masks pre-polished to 300~600 nm P-V flatness by CMP can then be improved down to 50~100 nm P-V flatness using the automated technology described in this paper. A series of edge polishing experiments also hints at the possibility of increasing the quality area beyond the 5 mm defined in the official EUV photomask specification.

Paper Details

Date Published: 9 September 2013
PDF: 6 pages
Proc. SPIE 8880, Photomask Technology 2013, 888018 (9 September 2013); doi: 10.1117/12.2026198
Show Author Affiliations
Anthony T. H. Beaucamp, Chubu Univ. (Japan)
Yoshiharu Namba, Chubu Univ. (Japan)
Phillip Charlton, Zeeko Ltd. (United Kingdom)
Richard R. Freeman, Zeeko Ltd. (United Kingdom)

Published in SPIE Proceedings Vol. 8880:
Photomask Technology 2013
Thomas B. Faure; Paul W. Ackmann, Editor(s)

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