Patent ID: 7678509

Claim:
A method of manufacturing a phase shift mask having, on a transparent substrate, a main opening formed by partly removing a light-shielding film and an auxiliary opening provided at a peripheral portion of said main opening, said auxiliary opening having a width incapable of being resolved when transferring, wherein the transparent substrate is partly removed in a depth direction such that phases of light passing through the main opening and light passing through the auxiliary opening differ from each other by a predetermined angle, comprising: a first process including a step of preparing a photomask blank having the light-shielding film, a thin film for forming an etching mask layer, and a first resist film which are formed in this order on the transparent substrate, said light-shielding film comprising a material being etchable by a fluorine-based etching medium, said thin film having a resistance to the fluorine-based etching medium, comprising a metal selected from chromium, tantalum, titanium, aluminum, hafnium, vanadium, or zirconium, an alloy of one or more of said metals, a metal compound containing one or more of oxygen, nitrogen, carbon, fluorine along with one of said metal or alloy, a step of exposing a pattern corresponding to the main opening and the auxiliary opening onto the first resist film and then developing to form a first resist pattern, a step of, using said first resist pattern as a mask, etching the thin film to form the etching mask layer, a step of, using the etching mask layer as a mask, etching the light-shielding film, and a step of stripping the remaining first resist pattern, a second process including a step of forming a second resist film on the transparent substrate obtained in the first process, a step of exposing a pattern corresponding to one of the main opening and the auxiliary opening and then developing to form a second resist pattern, a step of, using the second resist pattern as a mask, etching part of the transparent substrate to a depth such that the phases of the light passing through the main opening and the light passing through the auxiliary opening differ from each other by the predetermined angle, and a step of stripping the remaining second resist pattern, and a third process including a step of removing a part of or whole of the etching mask layer.