Patent ID: 7413832

Claim:
A method of producing a glass substrate for a mask blank, in which a surface of the glass substrate is polished by the use of a polishing liquid containing abrasive grains, wherein: the abrasive grains comprise colloidal silica abrasive grains produced by hydrolysis of an organosilicon compound, a content of alkali metal in the colloidal silica abrasive grains being 0.1 ppm or less, the polishing liquid has a pH value between 7.0 and 7.6, the glass substrate is one of a glass substrate for a phase shifi mask blank to be exposed by an ArF excimer laser, a glass substrate for a phase shift mask blank to be exposed by an F 2 excimer laser, and a glass substrate for a EUV reflective mask blank, the surface of the glass substrate is polished so as to have a surface roughness required in an exposure wavelength to be used so that a height of a protrusion on the surface of the glass substrate falls within a phase defect range that is allowable for the exposure wavelength, the protrusion being generated by an aggregate of the colloidal silica abrasive grains adhered to the surface of the glass substrate.