Patent ID: 7625677

Claim:
A photomask blank comprising a half-tone stacked film on a transparent substrate, wherein the half-tone stacked film includes: a phase advancement film, which advances the phase of light transmitted through the film compared to the case wherein the light is propagated in the air, and a phase retardation film, which retards the phase of light transmitted through the film compared to the case wherein the light is propagated in the air, stacked on or under the phase advancement film, wherein, the phase advancement film satisfies the relationship of k (+) >a 1 ·n (+) +b 1 , and the phase retardation film satisfies the relationship of k (−) <a 2 ·n (−) +b 2 , wherein, d (+) and d (−) are the film thickness in nanometers of the phase advancement film and phase retardation film respectively, n (+) and n (−) are the refractive index of the phase advancement film and phase retardation film respectively, k (+) and k (−) are the extinction coefficient of the phase advancement film and phase retardation film respectively, and a 1 =0.113·d (+) +0.774, b 1 =−0.116·d (+) −0.281, a 2 =0.113·d (−) +0.774, and b 2 =−0.116·d (−) −0.281; and wherein the absolute value of a phase difference between light transmitted in the half-tone stacked film and light propagated in the air is 50 degrees or less.