Membrane for EUV lithography
Membranes for EUV lithography are disclosed. In one arrangement, a membrane has a stack having layers in the following order: a first capping layer including an oxide of a first metal; a base layer including a compound having a second metal and an additional element selected from the group consisting of Si, B, C and N; and a second capping layer including an oxide of a third metal, wherein the first metal is different from the second metal and the third metal is the same as or different from the first metal.
1. A membrane for EUV lithography, the membrane comprising a stack having layers in the following order:
a first capping layer comprising an oxide of a first metal;
a base layer comprising a compound comprising a second metal and an additional element selected from the group consisting of Si, B, C and N; and
a second capping layer comprising an oxide of a third metal,
wherein the first metal is different from the second metal and the third metal is the same as or different from the first metal.
2. The membrane of claim 1 , wherein either or both of the first metal and the third metal is selected from the group consisting of Nb, Zr, Ce, Ti, La, Y, and Al.
3. The membrane of claim 1 , wherein in the compound of the base layer:
the second metal is Mo and the additional element is Si;
the second metal is Ru and the additional element is Si;
the second metal is Zr and the additional element is Si;
the second metal is La and the additional element is Si;
the second metal is Sc and the additional element is Si;
the second metal is Y and the additional element is Si;
the second metal is Nb and the additional element is Si;
the second metal is Mo and the additional element is B;
the second metal is Ru and the additional element is B;
the second metal is Zr and the additional element is B;
the second metal is Nb and the additional element is B;
the second metal is Ti and the additional element is B;
the second metal is La and the additional element is B; or
the second metal is Zr and the additional element is C.
4. The membrane of claim 3 , wherein in the compound of the base layer:
the second metal is Mo and the additional element is Si; or
the second metal is Ru and the additional element is Si.
5. The membrane of claim 3 , wherein in the compound of the base layer:
the second metal is Mo and the additional element is B; or
the second metal is Ru and the additional element is B.
6. The membrane of claim 1 , wherein in the base layer the compound comprising the second metal and the additional element consists of the second metal and the additional element.
7. The membrane of claim 1 , wherein:
the first metal is Zr;
the second metal is Mo and the additional element is Si; and
the third metal is Zr.
8. The membrane of claim 1 , wherein:
the oxide of the first metal is a mixed metal oxide comprising the first metal and one or more further metals;
the oxide of the third metal is a mixed metal oxide comprising the second metal and one or more further metals; or
the oxide of the first metal is a mixed metal oxide comprising the first metal and one or more further metals and the oxide of the third metal is a mixed metal oxide comprising the third metal and one or more further metals.
9. The membrane of claim 1 , wherein the base layer comprises plural base layer sub-layers, at least one of the base layer sub-layers comprising the compound comprising the second metal and the additional element.
10. The membrane of claim 9 , wherein:
the base layer comprises a base layer first sub-layer, a base layer second sub-layer and a base layer third sub-layer;
the base layer second sub-layer is disposed between the base layer first sub-layer and the base layer third sub-layer and comprises the compound comprising the second metal and the additional element;
the base layer first sub-layer comprises an oxide of the additional element; and the base layer third sub-layer comprises an oxide of the additional element.
11. The membrane of claim 10 , wherein at least a portion of the base layer first sub-layer is in contact with the oxide of the first metal in the first capping layer.
12. The membrane of claim 10 , wherein at least a portion of the base layer third sub-layer is in contact with the oxide of the third metal in the second capping layer.
13. The membrane of claim 1 , wherein at least a portion of the compound comprising the second metal and the additional element in the base layer is in contact with either or both of the oxide of the first metal in the first capping layer and the oxide of the third metal in the second capping layer.
14. The membrane of claim 1 , wherein the first capping layer comprises a first capping layer first sub-layer and a first capping layer second sub-layer, the first capping layer first sub-layer comprising the oxide of the first metal and the first capping layer second sublayer comprising a first capping layer deposited oxide, the first capping layer second sub-layer positioned between the first capping layer first sub-layer and the base layer.
15. The membrane of claim 14 , wherein the first capping layer deposited oxide comprises an oxide of silicon.
16. The membrane of claim 1 , wherein the second capping layer comprises a second capping layer first sub-layer and a second capping layer second sub-layer, the second capping layer first sub-layer comprising the oxide of the third metal and the second capping layer second sub-layer comprising a second capping layer deposited oxide,
the second capping layer second sub-layer positioned between the second capping layer first sub-layer and the base layer.
17. The membrane of claim 16 , wherein the second capping layer deposited oxide comprises an oxide of silicon.
18. The membrane of claim 1 , wherein the first capping layer and the second capping layer each has a thickness of less than 5 nm.
19. The membrane of claim 1 , wherein the base layer has a thickness equal to or greater than 8 nm.
20. The membrane of claim 19 , wherein the thickness of the base layer is selected to achieve destructive interference between EUV reflections from the first capping layer and the second capping layer.