Finishing of EUV photomask substrates by CNC precessed bonnet polisher

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

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Citations (Scopus)


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.

Original languageEnglish
Title of host publicationPhotomask Technology 2013
Publication statusPublished - 2013
Externally publishedYes
EventSPIE Conference on Photomask Technology 2013 - Monterey, CA, United States
Duration: 2013 Sept 102013 Sept 12

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceSPIE Conference on Photomask Technology 2013
Country/TerritoryUnited States
CityMonterey, CA


  • Corrective Polishing
  • Edge Polishing
  • EUV Photomask
  • Finishing
  • Full Factorial
  • Precessed Bonnet Polishing
  • Quality Area
  • Ultra- Precision

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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