Patent ID: 10871707

Abstract:
Provided is a reflective mask blank having a phase shift film for which there is little dependency of phase difference on film thickness. The reflective mask blank has a multilayer reflective film and a phase shift film, which causes a shift in the phase of EUV light, formed on a substrate in that order, wherein the phase shift film has an uppermost layer and a lower layer other than the uppermost layer and satisfies the following relationships: n2<n1<1 and λ/4×(2m+1)−α≤n1·d1≤λ/4×(2m+1)+α. (In the formulas, n1 represents the refractive index of the uppermost layer at an exposure wavelength of λ=13.5 nm, n2 represents the refractive index of the lower layer at an exposure wavelength of λ=13.5 nm, d1 represents the film thickness (nm) of the uppermost layer, m represents an integer of not less than 0, and α=1.5 nm).