| 摘要 |
A photomask blank is 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. 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. The photomask blank includes, on the digging-side surface of the light-transmitting substrate, an etching mask film 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. The photomask blank further includes, on a surface of the etching mask film, a light-shielding 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.
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