Reflective mask blank, reflective mask, reflective mask manufacturing method, and reflective mask correction method
There are provided a reflective mask blank, a reflective mask, a reflective mask manufacturing method, and a reflective mask correction technique capable of reducing time required for electron beam correction etching, even when a material used for a thin absorption film has a large extinction coefficient k to an EUV light. A reflective photomask blank ( 10 ) according to this embodiment has a substrate ( 1 ), a multi-layer reflective film ( 2 ), a capping layer ( 3 ), and a low reflective portion ( 5 ), in which the low reflective portion ( 5 ) is obtained by alternately depositing an absorption film (A) and an absorption film (B), the correction etching rate in the electron beam correction of the absorption film (A) is larger than the correction etching rate in the electron beam correction of the absorption film (B), and the absorption film (B) contains one or more elements selected from tin, indium, platinum, nickel, tellurium, silver, and cobalt.
1 . A reflective mask blank comprising:
a substrate;
a reflective film having a multi-layer film structure formed on the substrate and configured to reflect an EUV light;
a protective film formed on the reflective film and configured to protect the reflective film; and
an absorption film comprising a multi-layer film formed on the protective film and configured to absorb the EUV light, wherein
the absorption film is obtained by alternately depositing a first absorption film and a second absorption film, such that the first absorption film is in contact with the protective film and an outermost surface layer of the absorption film is the first absorption film,
under the presence of an etching gas, a correction etching rate in electron beam correction of the first absorption film is within a range of 20 times or more and 100 times or less a correction etching rate in electron beam correction of the second absorption film,
the first absorption film contains one or more elements selected from vanadium, cobalt, nickel, zirconium, niobium, and hafnium,
the second absorption film contains one or more elements selected from indium and platinum,
the surface roughness Ra of the reflective mask blank is less than 1.0 nm,
a total film thickness of the absorption film is 60 nm or less, and
a film thickness of the first absorption film is within a range of 0.5 nm or more and 6 nm or less.
2 . The reflective mask blank according to claim 1 , wherein at least one of the first absorption film or the second absorption film contains one or more types selected from nitrogen, oxygen, and carbon.
3 . The reflective mask blank according to claim 1 , wherein a film thickness of the second absorption film is 35 nm or less.
4 . A reflective mask comprising:
a substrate;
a reflective film having a multi-layer film structure formed on the substrate and configured to reflect an EUV light;
a protective film formed on the reflective film and configured to protect the reflective film; and
an absorption film comprising a multi-layer film formed on the protective film and configured to absorb the EUV light, wherein
a transfer pattern is formed on the absorption film,
the absorption film is formed by alternately depositing a first absorption film and a second absorption film, such that the first absorption film is in contact with the protective film and an outermost surface layer of the absorption film is the first absorption film,
under the presence of an etching gas, a correction etching rate in electron beam correction of the first absorption film is within a range of 20 times or more and 100 times or less a correction etching rate in electron beam correction of the second absorption film,
the first absorption film contains one or more elements selected from vanadium, cobalt, nickel, zirconium, niobium, and hafnium,
the second absorption film contains one or more elements selected from indium and platinum,
the surface roughness Ra of the reflective mask is less than 1.0 nm,
a total film thickness of the absorption film is 60 nm or less, and
a film thickness of the first absorption film is within a range of 0.5 nm or more and 6 nm or less.
5 . The reflective mask according to claim 4 , wherein at least one of the first absorption film or the second absorption film contains one or more types selected from nitrogen, oxygen, and carbon.
6 . The reflective mask according to claim 4 , wherein a film thickness of the second absorption film is 35 nm or less.
7 . The reflective mask according to claim 4 , comprising:
a projection portion and a depressed portion on a side surface on which the transfer pattern is formed of the second absorption film,
the projection portion being a most projecting portion in an in-plane direction of the second absorption film and the depressed portion being a most depressed portion in the in-plane direction of the second absorption film, wherein
when a distance from the projection portion to the depressed portion in the in-plane direction of the second absorption film is defined as a side etching amount, the side etching amount is 5 nm or less.
8 . The reflective mask according to claim 4 , further comprising:
an etching resistant film having a composition different from a composition of the second absorption film and configured to cover at least a part of a side surface on which the transfer pattern is formed of the second absorption film to protect the side surface of the second absorption film.
9 . A method for manufacturing the reflective mask according to claim 4 , the method comprising:
performing electron beam correction etching of the first absorption film; and
performing electron beam correction etching of the second absorption film, wherein
in the performing of the electron beam correction etching of the first absorption film, an etching resistant film is formed on a side surface of the second absorption film when the first absorption film is subjected to the electron beam correction etching, and
in the performing of the electron beam correction etching of the second absorption film, the second absorption film is subjected to the electron beam correction etching such that a side etching amount is 5 nm or less.
10 . A correction method by electron beam correction etching of the reflective mask according to claim 4 comprising:
performing electron beam correction of the first absorption film with an oxygen-containing etching gas; and
performing electron beam correction of the second absorption film with an oxygen-free etching gas.