Patent ReferencesMethod for producing silica glass Patent #: 4317668 InventorsAssigneeApplicationNo. 977397 filed on 05/15/1993US Classes:65/17.4, Including flame or gas contact501/54, More than 90 percent by weight silica501/900OPTICAL GLASS (E.G., SILENT ON REFRACTIVE INDEX AND/OR ABBE NUMBER)ExaminersPrimary: Bell, Mark L.Assistant: Bonner, C. M. Attorney, Agent or FirmForeign Patent References
International ClassC03C 003/06Foreign Application Priority Data1991-06-29 JPAbstractA synthetic quartz glass optical member for an ultraviolet laser, suitably applicable as a stepper lens of a lithographer using an excimer laser beam and other optical members, wherein the quartz glass has a hydroxyl content of 10 to 100 ppm, a chlorine content of 200 ppm or less, a hydrogen content of 1×1016 molecules/cm3 or less, a homogeneity of refractive index of 5×10-6 or less in terms of Ɗn, and a birefringence of 5 nm/cm or less. The optical member can be produced by subjecting a volatile silicon compound to flame hydrolysis with oxyhydrogen flame, depositing the formed particulate silica on a heat-resistant support to prepare a porous silica matrix, heating the matrix in a vacuum as high as 1×10-2 Torr or above to a temperature of 1,400 ° C. or above to effect dehydration and degassing, homogenizing the resultant transparent quartz glass into highly homogeneous quartz glass free from striae in at last one direction, molding the highly homogeneous quartz glass, and annealing the molded glass. | |