Synthetic quartz glass substrate for photomask and making method
AssigneeShin-Etsu Chemical Co., Ltd.
InventorsYukio Shibano, Hisatoshi Otsuka
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Abstract
A synthetic quartz glass substrate is prepared by annealing a synthetic quartz glass member having a higher hydroxyl content in a peripheral portion than in a central portion, machining off the peripheral portion of the member, slicing the member into a plate shaped substrate, chamfering and etching the substrate. The synthetic quartz glass substrate has a minimized birefringence and is suited for use as a photomask in photolithography.
Claims19
A synthetic quartz glass substrate for use as a photomask, obtained by annealing a synthetic quartz glass member having a higher hydroxyl content in a peripheral portion than in a central portion,
- wherein said central portion of said synthetic quartz glass member has a hydroxyl content of 400-600 ppm.
A method for preparing a synthetic quartz glass substrate comprising annealing a synthetic quartz glass member having a higher hydroxyl content in a peripheral portion than-in a central portion,
- wherein said central portion of said synthetic quartz glass member has a hydroxyl content of 400-600 ppm.
Dependencies are inferred from the claim text.