Reflective mask blank and reflective mask

Abstract

A reflective mask blank includes a substrate and, on or above the substrate in order, a reflective layer for reflecting EUV light, a protective layer for protecting the reflective layer, and an absorbent layer for absorbing EUV light. The absorbent layer has a reflectance for a wavelength of 13.53 nm of from 2.5% to 10% and consists of a lower absorption layer and an upper absorption layer. A film thickness dbi of the absorbent layer satisfies a relationship of: dbi MAX−(i×6+1) nm≤dbi≤dbi MAX−(i×6−1) nm where the integer i is 0 or 1, and dbi MAX is represented by: d bi ⁢ MAX ( nm ) = 13.53 2 ⁢ n ⁢ cos ⁢ 6 ⁢ ° { INT ( 0.58 1 - n 1 ) + 1 2 ⁢ π ⁢ ( tan - 1 ( - k 2 1 - n 2 ) + 0.64 ) } , where n1 is a refractive index of the lower absorbent layer, n2 is a refractive index of the upper absorbent layer, k2 is an absorption coefficient of the upper absorbent layer, and INT(x) is a function of returning an integer value obtained by truncating a decimal part.

Dependencies are inferred from the claim text.