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23 September 2013 Ultra-low roughness magneto-rheological finishing for EUV mask substrates
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EUV mask substrates, made of titania-doped fused silica, ideally require sub-Angstrom surface roughness, sub-30 nm flatness, and no bumps/pits larger than 1 nm in height/depth. To achieve the above specifications, substrates must undergo iterative global and local polishing processes. Magnetorheological finishing (MRF) is a local polishing technique which can accurately and deterministically correct substrate figure, but typically results in a higher surface roughness than the current requirements for EUV substrates. We describe a new super-fine MRF® polishing fluid whichis able to meet both flatness and roughness specifications for EUV mask blanks. This eases the burden on the subsequent global polishing process by decreasing the polishing time, and hence the defectivity and extent of figure distortion.
© (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Paul Dumas, Richard Jenkins, Chuck McFee, Arun J. Kadaksham, Dave K. Balachandran, and Ranganath Teki "Ultra-low roughness magneto-rheological finishing for EUV mask substrates", Proc. SPIE 8880, Photomask Technology 2013, 888005 (23 September 2013);

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