Patent ID: 7989122

Claim:
A photomask blank for manufacturing a phase shift mask having a light-transmitting substrate provided with a phase shift portion adapted to give a predetermined phase difference to transmitted exposure light, wherein the phase shift portion is a dug-down part that is dug down from a surface of the light-transmitting substrate to a digging depth adapted to produce the predetermined phase difference with respect to exposure light transmitted through the light-transmitting substrate at a portion where the phase shift portion is not provided, and the photomask blank comprises: an etching mask film, on a digging-side surface of the light-transmitting substrate, that is made of a material being dry-etchable with a chlorine-based gas, but not dry-etchable with a fluorine-based gas, and serves as an etching mask at least until, when forming the dug-down part by dry etching, the dry etching reaches the digging depth; and a light-shielding film, on a surface of the etching mask film, that is made of a material mainly containing tantalum and has a thickness so as to be removable during the dry etching for forming the dug-down part of the light-transmitting substrate.