Patent ID: 7767366

Claim:
A photomask blank from which is produced a photomask comprising a transparent substrate and a mask pattern formed thereon including transparent regions and effectively opaque regions to exposure light, said photomask blank comprising a transparent substrate, an etch stop film disposed on the substrate, optionally with another film intervening therebetween, said etch stop film of single layer or multilayer construction being resistant to fluorine dry etching and removable by chlorine dry etching, a light-shielding film disposed contiguous to said etch stop film and consisting of a single layer or multiple layers composed of a material containing a transition metal and silicon, and an antireflective film disposed contiguous to said light-shielding film and consisting of a single layer or multiple layers, wherein said transition metal is at least one element selected from the group consisting of titanium, vanadium, cobalt, nickel, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten, and an optical density OD of the combination of etch stop film, light-shielding film and antireflective film, or the combination of etch stop film, light-shielding film, antireflective film and said optional another film is at least 2.5.