Photomask blank, photomask and fabrication method thereof

摘要

A light-shieldable film (12) is formed on one principal plane of an optically transparent substrate (11), and the light-shieldable film (12) has a first light-shieldable film (13) and a second light-shieldable film (14) overlying the first light-shieldable film (13). The first light-shieldable film (13) is a film that is not substantially etched by fluorine-based (F-based) dry etching and is primarily composed of chromium oxide, chromium nitride, chromium oxynitride or the like. The second light-shieldable film (14) is a film that is primarily composed of a silicon-containing compound that can be etched by F-based dry etching, such as silicon oxide, silicon nitride, silicon oxynitride, silicon/transition-metal oxide, silicon/transition-metal nitride or silicon/transition-metal oxynitride.