Patent ID: 7625676

Claim:
A binary photomask blank, comprising a light-shieldable film formed on a substrate that is transparent to exposure light, the light-shieldable film comprising a first light-shieldable film formed on the substrate and a second light-shieldable film overlying the first light-shieldable film, wherein the first light-shieldable film is a film primarily composed of chromium metal, chromium oxide, chromium nitride, chromium oxynitride, chromium oxycarbide, chromium nitride carbide or chromium oxynitride carbide that is not substantially etched by fluorine-based dry etching and which has a thickness that is equal to or more than 3 nm and equal to or less than 15 nm, and wherein the second light-shieldable film having an antireflection capability comprises a layer primarily composed of a silicon-containing compound that is capable of being etched by fluorine-based dry etching, and wherein the optical density of the light-shieldable film comprising the stack of the first and second light-shieldable films to exposure light is 2.5 or higher.