US 12,216,398 B2
Reflective mask blank and reflective mask
Hiroyoshi Tanabe, Tokyo (JP); Hiroshi Hanekawa, Tokyo (JP); and Toshiyuki Uno, Tokyo (JP)
Assigned to AGC INC., Tokyo (JP)
Filed by AGC INC., Tokyo (JP)
Filed on Jan. 19, 2024, as Appl. No. 18/417,352.
Application 18/417,352 is a continuation of application No. 17/658,763, filed on Apr. 11, 2022, granted, now 11,914,283.
Application 17/658,763 is a continuation of application No. PCT/JP2020/040115, filed on Oct. 26, 2020.
Claims priority of application No. 2019-195856 (JP), filed on Oct. 29, 2019.
Prior Publication US 2024/0176225 A1, May 30, 2024
Int. Cl. G03F 1/24 (2012.01); G03F 1/52 (2012.01); G03F 1/54 (2012.01)
CPC G03F 1/24 (2013.01) [G03F 1/52 (2013.01); G03F 1/54 (2013.01)] 9 Claims
 
1. A reflective mask blank comprising 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,
wherein the absorbent layer has a reflectance for a wavelength of 13.53 nm of from 2.5% to 10%,
the absorbent layer consists of two layers of a lower absorbent layer and an upper absorbent layer, and
a film thickness dbi of the absorbent layer consisting of the two layers satisfies a relationship of:
dbi MAX−(i×6+1) nm≤dbi≤dbi MAX−(i×6−1) nm
wherein the integer i is 0 or 1, and dbi MAX is represented by:

OG Complex Work Unit Math
wherein 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.