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Proceedings Paper

Homogeneity improvement of TiO2-SiO2 glass synthesized by the soot method and its evaluation using the ultrasonic measurement system
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Paper Abstract

TiO2-SiO2 glass is one of the leading candidates for optical elements of extreme ultraviolet lithography. TiO2-SiO2 glass synthesized by the soot method has shown striae related to inhomogeneity of TiO2 concentration formed in the planes perpendicular to soot growth direction in the synthesis process. It can induce CTE variation and localized surface roughness. Striae were characterized in three modes by polarization microscope. Such striae were improved with an improved gas condition and developing a modified material gas supply system. Specimen prepared from the improved TiO2-SiO2 glass was evaluated by a line-focus-beam ultrasonic material characterization system, using a surface-acoustic-wave mode. Improved glass had 43% striae level compared to conventional glass by birefringence measurement, 31% compared to conventional glass by the ultrasonic measurement. It was found that improved glass had good homogeneity to both directions perpendicular and parallel to striae plane.

Paper Details

Date Published: 1 April 2013
PDF: 7 pages
Proc. SPIE 8679, Extreme Ultraviolet (EUV) Lithography IV, 86791N (1 April 2013); doi: 10.1117/12.2011655
Show Author Affiliations
Masahiro Kawagishi, Asahi Glass Co., Ltd. (Japan)
Junko Konishi, Asahi Glass Co., Ltd. (Japan)
Masaaki Takata, Asahi Glass Co., Ltd. (Japan)
Mototaka Arakawa, Tohoku Univ. (Japan)
Yuji Ohashi, Tohoku Univ. (Japan)
Jun-ichi Kushibiki, Tohoku Univ. (Japan)

Published in SPIE Proceedings Vol. 8679:
Extreme Ultraviolet (EUV) Lithography IV
Patrick P. Naulleau, Editor(s)

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