Patent ID: 7955762

Claim:
A photomask blank comprising: a transparent substrate and a film containing at least two layers formed on the transparent substrate, the two layers being a phase-difference reduction layer with a phase difference Δθ 1 being negative and a layer with a phase difference Δθ 2 being positive, wherein the phase difference Δθ 1 is a phase difference between a light transmitted through the phase-difference reduction layer and a light transmitted through an air distance equal to a thickness of the phase-difference reduction layer, wherein the phase difference Δθ 2 is a phase difference between a light transmitted through the layer with the phase difference Δθ 2 being positive and a light transmitted through an air distance equal to a thickness of the layer with the phase difference Δθ 2 being positive, and wherein the phase difference Δθ 1 and the phase difference Δθ 2 are canceled out, and a phase difference of the film containing at least two layers is from −30° to +30°.