US 12,235,575 B2
Reflective mask blank for EUV lithography and substrate with conductive film
Yusuke Ono, Fukushima (JP); Hiroshi Hanekawa, Fukushima (JP); and Hirotomo Kawahara, Tokyo (JP)
Assigned to AGC INC., Tokyo (JP)
Filed by AGC INC., Tokyo (JP)
Filed on Feb. 12, 2024, as Appl. No. 18/439,057.
Application 18/439,057 is a continuation of application No. 18/219,452, filed on Jul. 7, 2023, granted, now 11,934,093.
Application 18/219,452 is a continuation of application No. PCT/JP2022/034854, filed on Sep. 16, 2022.
Claims priority of application No. 2021-157976 (JP), filed on Sep. 28, 2021.
Prior Publication US 2024/0184191 A1, Jun. 6, 2024
Int. Cl. G03F 1/24 (2012.01)
CPC G03F 1/24 (2013.01) 28 Claims
 
1. A reflective mask blank for EUV lithography, comprising:
a substrate;
a conductive film disposed on or above a back surface of the substrate;
a reflective layer disposed on or above a front surface of the substrate, the reflective layer reflecting EUV light; and
an absorption layer disposed on or above the reflective layer, the absorption layer absorbing the EUV light,
wherein the conductive film has a refractive index nλ1000-1100 nm of 5.300 or less and has an extinction coefficient kλ1000-1100 nm of 5.200 or less, at a wavelength of 1000 nm to 1100 nm,
the conductive film has a refractive index nλ600-700 nm of 4.300 or less and has an extinction coefficient kλ600-700 nm of 4.500 or less, at a wavelength of 600 nm to 700 nm, and
the conductive film has a light transmittance at the wavelength of 1000 nm to 1100 nm of 2.0% or more, a light transmittance at the wavelength of 600 nm to 700 nm of 1.0% or more, and a light transmittance at a wavelength of 400 nm to 500 nm of less than 1.0%.