Photomask substrate plate of synthetic fused silica glass for photolithography.

摘要

A photomask substrate plate of synthetic fused silica glass for use in photolithography can be imparted with remarkably improved stability relative to the transmissivity to ultraviolet light and to the dimensional changes due to so-called "radiation compaction" under irradiation, in particular, with ultraviolet light of short wavelength, such as the light emitted from an ArF excimer laser, when the content of molecular hydrogen in the fused silica glass is in the range from 1x10<1><7> to 1x10<1><9> molecules/cm<3>. The content of molecular hydrogen can be controlled within the specified range by suitably selecting the conditions used in the preparation of silicon dioxide by the direct flame hydrolysis method and the annealing treatment.