Preparation of fused silica glass by hydrolysis of methyl silicate
AssigneeShin-Etsu Chemical Co., Ltd.
InventorsMasatoshi Takita, Takaaki Shimizu
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Abstract
The invention provides a method for the preparation of synthetic fused silica glass containing a very small amount of hydroxyl groups and has a high viscosity at high temperatures suitable for use as a material of articles for semiconductor processing at high temperatures, such as a crucible for Czochralski single crystal growing of semiconductor silicon. The method comprises hydrolyzing methyl silicate in a medium containing a specified amount of ammonia as a hydrolysis catalyst to form silica particles which are heat-treated in several successive steps.
Claims4
A method for the preparation of fused silica glass which comprises the successive steps of:
- (a) adding methyl silicate to water as a hydrolysis medium containing ammonia as a catalyst to effect hydrolysis of the methyl silicate forming agglomerated silica particles;
- (b) separating the silica particles from the hydrolysis medium;
- (c) heating the silica particles in an oxidizing atmosphere to oxidize and remove organic materials contained therein at a temperature of from 300.degree. to 1000.degree. C.;
- (d) sintering the silica particles by heating at a temperature in the range from 1500.degree. to 1850.degree. C.;
- (e) pulverizing the sintered silica particles into a silica powder;
- (f) washing the silica powder with an acid;
- and
- (g) shaping and sintering the silica powder after washing with said acid by heating at a temperature of 1700.degree. C. or higher to form said silica glass.
Dependencies are inferred from the claim text.