Patent ID: 8931307
Filing Date: 2015-01-13
Classification: C03B,C03C,G02B,G03F,Y10T

Abstract:
1. A method for producing a blank of titanium-doped, highly siliceous glass suitable for use as a mirror substrate used in extreme ultra violet lithography, wherein said blank has a surface area that has an outer contour to be metalized, and said surface area is specified as a highly stressed zone during the use of the mirror substrate, the method comprising the following steps: (a) producing a front body of titanium-doped glass of high homogeneity with a first volume and with dimensions enclosing the outer contour with an oversize; (b) producing a support body of titanium-doped quartz glass with a second volume, the support body being a monolithic glass block of lower homogeneity than the front body; (c) joining front body and support body so as to form a composite body; and (d) treating the composite body so as to obtain the mirror substrate blank, wherein the producing of the front body includes a homogenizing process which comprises a twisting process of a rod-shaped start body obtained by flame hydrolysis of a silicon-containing compound so as to form a front body blank, wherein the start body is held during the twisting process between two holders, and the start body is zonewise heated to melting temperature and the heated zone is thereby worked by relative movement of the two holders with respect to each other so as to form a substantially cylindrical twist body.