Transparent substrate for mask blank and mask blank

Abstract

In a transparent substrate for a mask blank, which is required to have a predetermined optical characteristic, a substrate mark is formed by cutting off a predetermined corner portion into an oblique section. The shape of the mark is determined in accordance with the optical characteristic of he substrate.

1 . A transparent substrate for a mask blank, which is required to have a predetermined optical characteristic, comprising:
 a substrate mark formed by cutting off a predetermined corner portion into an oblique cross section,   the substrate mark having a shape determined in accordance with the optical characteristic.   
   
   
       2 . A transparent substrate as claimed in  claim 1 , wherein:
 the substrate mark is formed by combining a plurality of oblique sections.   
   
   
       3 . A transparent substrate as claimed in  claim 1 , wherein:
 the optical characteristic is transmittance for an exposure wavelength and/or variation of transmittance in a substrate plane.   
   
   
       4 . A transparent substrate as claimed in  claim 1 , wherein:
 the exposure wavelength falls within a range between 140 nm and 200 nm.   
   
   
       5 . A transparent substrate as claimed in  claim 1 , wherein:
 a material of the transparent substrate is a synthetic quartz glass.