Patent ID: 11187974

Abstract:
A photomask blank and a photomask having favorable wafer transfer characteristics and irradiation resistance. A photomask blank is for fabricating a photomask for an exposure wavelength of 193 nm, the photomask blank comprising: a light-transmissive substrate; a phase shift film formed on the light-transmissive substrate and providing phase shift effects of a light transmittance of at least 30% with respect to exposure light; and a light-shielding film formed on the phase shift film. The phase shift film is constituted by lamination of: a first phase shift film (that uses a silicon nitride-based material, has a refractive index n1 of 2.5 to 2.7, and an extinction coefficient k1 of 0.2 to 0.4; and a second phase shift film that uses a silicon oxynitride-based material, has a refractive index n2 of 1.55 to 2.20, and an extinction coefficient k2 greater than 0 but no greater than 0.1.