Patent ID: 8048594

Claim:
A photomask blank for fabricating a phase shift mask having a light-transmissive substrate provided with a phase shift part adapted to give a predetermined phase difference to transmitted exposure light, wherein said phase shift part is a dug-down part formed by digging down said light-transmissive substrate from a surface thereof to a digging depth adapted to produce the predetermined phase difference with respect to exposure light transmitted through said light-transmissive substrate at a portion where said phase shift part is not provided, said photomask blank comprising: a light-shielding part not formed on a surface of a transfer pattern area of said light-transmissive substrate but formed in contact with a surface of a peripheral area around the transfer pattern area and adapted to shield exposure light; and an etching mask film formed in contact with the surface of the transfer pattern area and with an upper surface of the light-shielding part, wherein the light-shielding part is made of a material containing metal, and wherein said etching mask film is made of a material containing metal which is substantially dry-etchable with a chlorine-based gas, but not substantially dry-etchable with a fluorine-based gas, said etching mask film serving as an etching mask at least until said digging depth is reached when forming said dug-down part.