	US 12,105,412 B2
	Reflective mask blank, reflective mask, method of manufacturing reflective mask blank, and method of manufacturing reflective mask
Daijiro Akagi, Tokyo (JP); Hiroaki Iwaoka, Tokyo (JP); Wataru Nishida, Tokyo (JP); Ichiro Ishikawa, Tokyo (JP); and Kenichi Sasaki, Tokyo (JP)
Assigned to AGC Inc., Tokyo (JP)
Filed by AGC Inc., Tokyo (JP)
Filed on Feb. 16, 2024, as Appl. No. 18/444,020.
Application 18/444,020 is a continuation of application No. PCT/JP2022/047930, filed on Dec. 26, 2022.
Claims priority of application No. 2021-214753 (JP), filed on Dec. 28, 2021.
Prior Publication US 2024/0272541 A1, Aug. 15, 2024
Int. Cl. G03F 1/24 (2012.01)

CPC G03F 1/24 (2013.01)

14 Claims

1. A reflective mask blank for EUV lithography comprising:

a substrate;

a multilayer reflective film that reflects EUV light;

a protection film that protects the multilayer reflective film; and

an absorption film that absorbs the EUV light, in this order from bottom to top, wherein

the protection film includes an upper layer made of a rhodium-based material comprising Rh, or comprising Rh and at least one element selected from a group consisting of N, O, C, B, Ru, Nb, Mo, Ta, Ir, Pd, Zr, and Ti, the rhodium-based material containing 50 at % to 100 at % of Rh; and a lower layer containing at least one element selected from a group consisting of Ru, Nb, Mo, Zr, Y, C, and B, and satisfying a condition (I) in an EUV region

k<−0.15n+0.16 (I)

where n represents a refractive index and k represents an extinction coefficient.