Heraeus Quarzglas Gmbh & Co Kg

Stephan Ochs

Bodo Kuehn

Steffen Kaiser

Denis Kassube

A known method for producing synthetic quartz glass with a predetermined hydroxyl group content comprises the following steps: a porous SiOsoot body is produced by flame hydrolysis or oxidation of a silicon-containing start compound and by layerwise deposition of SiOparticles on a rotating support; the soot body is subjected to a dehydration treatment in a reaction gas-containing drying atmosphere at a drying temperature for removing hydroxyl groups; and the SiOsoot body is vitrified into a body consisting of the synthetic quartz glass. Starting from this, and in order to permit a reproducible and reliable manufacture of synthetic, UV-radiation resistant quartz glass with predetermined hydroxyl group content and low chlorine content, it is suggested according to the invention that the dehydration treatment according to method step (b) comprises a drying phase during which ozone is used as the reaction gas, whereby the ozone content of the drying atmosphere is between 0.5% by vol. and 10% by vol. and the drying temperature is chosen in the range between 1200&#xb0; C. and 1400&#xb0; C., and whereby no halogens are supplied to the drying atmosphere.

Method for producing synthetic quartz glass with predetermined hydroxyl group content

To provide an optical component of quartz glass for use in a projection lens system for immersion lithography with an operating wavelength below 250 nm, which is optimized for use with linearly polarized UV laser radiation and particularly with respect to compaction and birefringence induced by anisotropic density change, it is suggested according to the invention that the quartz glass should show the combination of several properties: particularly a glass structure essentially without oxygen defects, a mean content of hydroxyl groups of less than 60 wt ppm, a mean content of fluorine of less than 10 wt ppm, a mean content of chlorine of less than 1 wt ppm. A method for producing such an optical component comprises the following method steps: producing and drying an SiOsoot body under reducing conditions and treating the dried soot body before or during vitrification with a reagent reacting with oxygen defects of the quartz glass structure.

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Bad Camberg, Germany

Stephan Ochs