Patent ID: 8323858

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 portion 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: the light transmitting substrate; and a light shieldable film formed on the light transmitting substrate, wherein the light shieldable film comprises: a light shielding layer which is formed of molybdenum silicide metal having a molybdenum content greater than 20 atomic % and not greater than 40 atomic % and which has a thickness smaller than 40 nm; an antireflection layer formed on the light shielding layer in contact with the light shielding layer and comprising a molybdenum silicide compound containing at least one of oxygen and nitrogen; and a low reflection layer formed under the light shielding layer in contact with the light shielding layer, wherein the low reflection layer is formed of a material having an etching selectivity for an etching gas used in digging the light transmitting substrate by dry etching and is formed in contact with a dug-down surface of the light transmitting substrate.