US 12,265,321 B2
Reflective mask blank, and method for manufacturing reflective mask
Takuro Kosaka, Joetsu (JP); Taiga Ogose, Joetsu (JP); Yukio Inazuki, Joetsu (JP); and Hideo Kaneko, Joetsu (JP)
Assigned to SHIN-ETSU CHEMICAL CO., LTD., Tokyo (JP)
Filed by Shin-Etsu Chemical Co., Ltd., Tokyo (JP)
Filed on May 31, 2022, as Appl. No. 17/828,702.
Claims priority of application No. 2021-101287 (JP), filed on Jun. 18, 2021.
Prior Publication US 2022/0404694 A1, Dec. 22, 2022
Int. Cl. G03F 1/24 (2012.01)
CPC G03F 1/24 (2013.01) 8 Claims
 
1. A reflective mask blank which is a material for a reflective mask used in EUV lithography using EUV light as exposure light, comprising a substrate, a multilayer reflection film that is formed on one main surface of the substrate and reflects the exposure light, a protection film formed in contact with the multilayer reflection film, and an absorber film that is formed on the protection film and absorbs the exposure light, wherein
the multilayer reflection film has a periodically laminated structure in which low-refractive index layers composed of a material comprising molybdenum (Mo) and high-refractive index layers are alternately laminated,
the low-refractive index layer consists of one or more of first low-refractive index sublayers, and one or more of second low-refractive index sublayers that have a different composition from a composition of the first low-refractive index sublayer,
the first low-refractive index sublayer comprises molybdenum (Mo), and one or more elements selected from the group consisting of nitrogen (N), carbon (C), hydrogen (H) and boron (B),
the second low-refractive index sublayer comprises either of both of molybdenum (Mo) and carbon, and is free of nitrogen (N), hydrogen (H) and boron (B),
the second low-refractive index sublayer has a thickness of not less than 0.1 nm and not more than 0.5 nm, and
in the low-refractive index layer, either or both of the low-refractive index sublayers that are in contact with the high-refractive index layer are the second low-refractive index sublayer.