Method for depositing a cover layer, EUV lithography system and optical element
A method of depositing a cover layer onto an optical element (M 1 ) for reflection of EUV radiation. In the method, a cover layer containing phosphorus (P) is deposited onto the optical element (M 1 ). The optical element (M 1 ) in the course of deposition of the cover layer ( 35 ) is disposed in an interior ( 39 ) of a housing ( 36 ) of an EUV lithography system, and, for the deposition of the cover layer, phosphorus (P) is released from at least one phosphorus source ( 42, 43 ) disposed outside the interior ( 39 ) or within the interior ( 39 ). Also disclosed are an EUV lithography system and an optical element (M 1 ) for reflecting EUV radiation.
1 . A method, comprising:
depositing a cover layer containing phosphorus onto an optical element; wherein, in the course of said depositing of the cover layer, the optical element is disposed in an interior of a housing of an extreme ultraviolet (EUV) lithography system; and
for said depositing of the cover layer, releasing phosphorus from at least one phosphorus source disposed outside the interior or within the interior, wherein the cover layer is deposited onto a protective layer of the optical element.
2 . The method as claimed in claim 1 , wherein the cover layer has a phosphorus content of at least 95 at %.
3 . The method as claimed in claim 1 , wherein the cover layer has a thickness of between 0.3 nm and 5 nm.
4 . The method as claimed in claim 1 , wherein the protective layer includes at least one precious metal.
5 . The method as claimed in claim 1 , wherein said depositing of the cover layer comprises feeding at least one gas containing phosphorus to the interior via at least one gas inlet.
6 . The method as claimed in claim 5 , wherein said feeding of the gas containing phosphorus comprises admixing the gas with at least one purge gas.
7 . The method as claimed in claim 6 , wherein the purge gas is hydrogen.
8 . The method as claimed in claim 5 , wherein the phosphorus fed to the interior has a partial pressure in the interior of at least 10 −6 mbar.
9 . The method as claimed in claim 1 , wherein said releasing of the phosphorus comprises exposing a source of the phosphorus to a hydrogen plasma which is generated in operation of the EUV lithography system.
10 . The method as claimed in claim 1 , further comprising:
removing a carbon contamination layer from a surface of the optical element prior to said depositing of the cover layer.
11 . The method as claimed in claim 10 , wherein the carbon contamination layer is removed from the surface by a hydrogen plasma generated in operation of the EUV lithography system.
12 . The method as claimed in claim 10 , wherein the carbon contamination layer is removed from the surface of the optical element by at least one cleaning head.
13 . The method as claimed in claim 12 , wherein the at least one cleaning head generates a hydrogen plasma.
14 . A method, comprising:
depositing a cover layer containing phosphorus onto an optical element; wherein, in the course of said depositing of the cover layer, the optical element is disposed in an interior of a housing of an extreme ultraviolet (EUV) lithography system; and
for said depositing of the cover layer, releasing phosphorus from at least one phosphorus source disposed outside the interior or within the interior,
wherein said depositing of the cover layer comprises feeding at least one gas containing phosphorus to the interior via at least one gas inlet, and
wherein said feeding of the gas containing phosphorus comprises admixing the gas with at least one purge gas.
15 . The method as claimed in claim 14 , wherein the purge gas is hydrogen.
16 . The method as claimed in claim 15 , wherein the phosphorus fed to the interior has a partial pressure in the interior of at least 10 −6 mbar.
17 . A method, comprising:
depositing a cover layer containing phosphorus onto an optical element; wherein, in the course of said depositing of the cover layer, the optical element is disposed in an interior of a housing of an extreme ultraviolet (EUV) lithography system; and
for said depositing of the cover layer, releasing phosphorus from at least one phosphorus source disposed outside the interior or within the interior,
wherein said releasing of the phosphorus comprises exposing a source of the phosphorus to a hydrogen plasma which is generated in operation of the EUV lithography system.
18 . A method, comprising:
removing a carbon contamination layer from a surface of an optical element;
subsequent to the removing, depositing a cover layer containing phosphorus onto the optical element; wherein, in the course of said depositing of the cover layer, the optical element is disposed in an interior of a housing of an extreme ultraviolet (EUV) lithography system; and
for said depositing of the cover layer, releasing phosphorus from at least one phosphorus source disposed outside the interior or within the interior.
19 . The method as claimed in claim 18 , wherein the carbon contamination layer is removed from the surface by a hydrogen plasma generated in operation of the EUV lithography system.
20 . The method as claimed in claim 18 , wherein the carbon contamination layer is removed from the surface of the optical element by at least one cleaning head.
21 . The method as claimed in claim 20 , wherein the at least one cleaning head generates a hydrogen plasma.