Finishing of EUV photomask substrates by CNC precessed bonnet polisher

Anthony T. H. Beaucamp; Yoshiharu Namba; Phillip Charlton; Richard R. Freeman

doi:10.1117/12.2026198

9 September 2013 Finishing of EUV photomask substrates by CNC precessed bonnet polisher

Anthony T. H. Beaucamp, Yoshiharu Namba, Phillip Charlton, Richard R. Freeman

Proceedings Volume 8880, Photomask Technology 2013; 888018 (2013) https://doi.org/10.1117/12.2026198
Event: SPIE Photomask Technology, 2013, Monterey, California, United States

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.

Citation Download Citation

Anthony T. H. Beaucamp, Yoshiharu Namba, Phillip Charlton, and Richard R. Freeman "Finishing of EUV photomask substrates by CNC precessed bonnet polisher", Proc. SPIE 8880, Photomask Technology 2013, 888018 (9 September 2013); https://doi.org/10.1117/12.2026198

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