BLANK MADE OF TITANIUM-DOPED SILICA GLASS FOR A MIRROR SUBSTRATE FOR USE IN EUV LITHOGRAPHY AND METHOD FOR THE PRODUCTION THEREOF

摘要

The present invention relates to a blank constituted of titanium-doped silica glass for a mirror substrate for being used in EUV lithography, and to a manufacturing method thereof. The blank is equipped with an optically used area (CA) having a surface unit provided with a reflective membrane. A coefficient of thermal expansion (CTE) in the CA includes a two-dimensional dCTE distribution profile standardized through the thickness of the blank having maximum heterogeneity (dCTEmax) less than 5 ppb/K defined as the difference between a CTE maximum value and a CTE minimum value. The purpose of the present invention is to be used with a non-circular irradiation profile, without control of titanium oxide concentrations dependent on an individually adapted position.