Patent ID: 7115341

Claim:
A halftone phase shift mask blank for use in manufacturing a halftone phase shift mask comprising a transparent substrate, a light transmitting portion formed on the substrate for transmitting an exposure light beam, a phase shifter portion formed on the substrate for transmitting a part of the exposure light beam as a transmitted light beam and for shifting a phase of the transmitted light beam by a predetermined amount, the halftone phase shift mask being designed so that light beams passing through the light transmitting portion and through the phase shifter portion cancel each other in the vicinity of a boundary portion therebetween, thereby keeping a predetermined contrast at a boundary portion of an exposure pattern to be transferred onto the surface of an object to be exposed, wherein: the halftone phase shift mask blank comprises a phase shifter film for forming the phase shifter portion on the transparent substrate; the phase shifter film comprises at least an upper layer to be etched by dry etching using a fluorine-based gas and a lower layer which is formed between the upper layer and the transparent substrate, which is resistant against the fluorine-based gas, and which can be etched by dry etching using a gas different from the fluorine-based gas; wherein (1) the lower layer is made of a single metal selected from a first group consisting of Al, Ga, Hf, Ti, V, and Zr or a first material containing two or more of said metals from the first group, or (2) the lower layer is made of a second material comprising at least one metal selected from a second group consisting of Cr, Ge, Pd, Si, Ta, Nb, Sb, Pt, Au, Po, Mo, and W with at least one metal selected from the group added thereto, or (3) the lower layer is made of a third material comprising (a) a single selected from the first group with nitrogen and/or carbon added thereto, or (b) the first material with nitrogen and/or carbon added thereto, or (c) the second material with nitrogen and/or carbon added thereto.