Asahi Glass Company, Limited

Keigo Hino

Shinya Kikugawa

Hitoshi Mishiro

An object of the invention is to provide a process for producing a synthetic quartz glass while taking account of a refractive index distribution remaining in the synthetic quartz glass; a jig for use in the synthetic-quartz-glass production process; and a synthetic quartz glass for an optical member, produced by the process. A process for producing a synthetic quartz glass, which comprises: depositing and growing fine quartz glass particles synthesized by flame hydrolysis of a glass-forming material on a rotating target to thereby form a porous quartz glass base of a substantially cylindrical shape; presintering the porous quartz glass base; and heating the presintered porous quartz glass base to a temperature not lower than the vitrification temperature to convert the base into a transparent glass, wherein in the step of conversion into a transparent glass, the porous quartz glass base is placed so as to make its growth axis vertical and a load is vertically imposed on the thus-placed porous quartz glass base.

Process for producing synthetic quartz glass

The invention provides a process for producing a synthetic quartz glass, comprising: (a) depositing fine quartz glass particles synthesized by flame hydrolysis of a glass-forming material, on a substrate, to form a porous quartz glass base; (b) presintering the porous quartz glass base; (c) heat-treating the presintered porous quartz glass base by holding it under vacuum at a temperature in the range of from 1,100&#xb0; C. to below the vitrification temperature for a certain time period; and (d) heating the thus heat-treated porous quartz glass base to a temperature not lower than the vitrification temperature to obtain a synthetic quartz glass. According to the process for synthetic quartz glass production of the invention, a synthetic quartz glass having a reduced OH group amount and a uniform OH group concentration can be obtained. From the synthetic quartz glass, an optical member having excellent optical properties can be obtained.

Process for producing synthetic quartz glass and synthetic quartz glass for optical member

It is to provide a photomask substrate which has a low birefringence and with which polarized illumination can be employed or immersion exposure can be carried out. A photomask substrate made of a synthetic quartz glass to be used for production of a semiconductor employing a light source having an exposure wavelength of at most about 200 nm, which has a birefringence of at most 1 nm/6.35 mm at the exposure wavelength, and of which the amount of decrease in light transmittance is at most 1.0% as a difference in light transmittance at a wavelength of 217 nm, between before and after irradiation with Xe excimer lamp with an illuminance of 13.2 mW/cmfor 20 minutes.

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Koriyama, Japan

Keigo Hino