Reflective optical element for grazing incidence in the EUV wavelength range
An optical element comprises a reflecting coating on a substrate. The reflecting coating contains boron and can have a thickness of more than 50 nm.
1. An optical element, comprising:
a substrate; and
a reflecting coating supported by the substrate,
wherein:
the reflecting coating comprises a layer that comprises a metal boride;
the metal boride comprises at least one metal selected from the group consisting of molybdenum, ruthenium, niobium, zirconium, rhodium, rhenium, palladium, gold, platinum, nickel, osmium, iridium, titanium, magnesium, calcium and strontium;
the layer has a thickness of more than 50 nm; and
the reflecting coating has a reflectivity of at least 60% for EUV radiation.
2. The optical element of claim 1 , wherein the optical element is a grazing incidence optical element.
3. The optical element of claim 1 , wherein the metal boride comprises a mixed metal boride.
4. The optical element of claim 3 , wherein the mixed metal boride is a binary metal boride or ternary metal boride.
5. The optical element of claim 1 , wherein the metal boride has a stoichiometry which varies over the thickness of the reflecting coating.
6. The optical element of claim 1 , wherein the substrate comprises a material which comprises a material selected from the group consisting of a metal, a metal alloy, a glass, a glass ceramic, a ceramic, a monocrystalline semiconductor, a polycrystalline semiconductor, and a composite material.
7. The optical element of claim 1 , further comprising an adhesion promoter layer between the substrate and the reflecting coating.
8. The optical element of claim 1 , further comprising an adhesion promoter layer between the substrate and the reflecting coating, wherein the adhesion promoter layer comprises a metal of the metal boride.
9. The optical element of claim 1 , further comprising an adhesion promoter layer between the substrate and the reflecting coating, wherein the metal boride comprises a mixed metal boride, and the adhesion promoter layer comprises a metal of the mixed metal boride.
10. The optical element of claim 1 , wherein the thickness of the layer is more than 100 nm.
11. The optical element of claim 1 , wherein the thickness of the layer is more than 1000 nm.
12. The optical element of claim 1 , wherein the reflecting coating comprises only one layer that contains the metal boride.
13. The optical element of claim 1 , wherein the reflecting coating consists of the layer.
14. The optical element of claim 1 , wherein the optical element is a collector mirror.
15. The optical element of claim 1 , wherein the reflectivity of the reflecting coating is at least 60% for EUV radiation when an angle of incidence of the EUV radiation with the reflecting layer is up to 24.5°.
16. The optical element of claim 15 , wherein the reflectivity of the reflecting coating is at least 60% for EUV radiation when the angle of incidence of the EUV radiation with the reflecting layer is at least 15°.
17. An optical system, comprising:
an optical element, comprising:
a substrate; and
a reflecting coating supported by the substrate,
wherein:
the reflecting coating comprises a layer that comprises a metal boride;
the metal boride comprises at least one metal selected from the group consisting of molybdenum, ruthenium, niobium, zirconium, rhodium, rhenium, palladium, gold, platinum, nickel, osmium, iridium, titanium, magnesium, calcium and strontium;
the layer has a thickness of more than 50 nm;
the reflecting coating has a reflectivity of at least 60% for EUV radiation; and
the optical system is an EUV lithography optical system.
18. The optical system of claim 17 , wherein the optical element is a grazing incidence optical element.
19. The optical system of claim 17 , wherein the system is an EUV lithography illumination system.
20. The optical system of claim 17 , wherein the reflecting coating comprises only one layer that contains the metal boride.
21. The optical element of claim 17 , wherein the reflectivity of the reflecting coating is at least 60% for EUV radiation when an angle of incidence of the EUV radiation with the reflecting layer is up to 24.5°.
22. The optical element of claim 21 , wherein the reflectivity of the reflecting coating is at least 60% for EUV radiation when the angle of incidence of the EUV radiation with the reflecting layer is at least 15°.
23. A device, comprising:
an illumination system; and
a projection objective,
wherein:
the device comprises an optical element;
the optical element comprises a substrate and a reflecting coating supported by the substrate;
the reflecting coating comprises a layer that comprises a metal boride;
the metal boride comprises at least one metal selected from the group consisting of molybdenum, ruthenium, niobium, zirconium, rhodium, rhenium, palladium, gold, platinum, nickel, osmium, iridium, titanium, magnesium, calcium and strontium;
the layer has a thickness of more than 50 nm;
the reflecting coating has a reflectivity of at least 60% for EUV radiation; and
the device is an EUV lithography device.
24. The device of claim 23 , wherein the illumination system comprises the optical element.
25. The device of claim 23 , wherein the reflecting coating comprises only one layer that contains the metal boride.
26. The device of claim 23 , wherein the reflectivity of the reflecting coating is at least 60% for EUV radiation when an angle of incidence of the EUV radiation with the reflecting layer is up to 24.5°.
27. The device of claim 26 , wherein the reflectivity of the reflecting coating is at least 60% for EUV radiation when the angle of incidence of the EUV radiation with the reflecting layer is at least 15°.
28. An optical element, comprising:
a substrate; and
a reflecting coating supported by the substrate,
wherein:
only one layer of the reflecting coating comprises a mixed metal boride:
the mixed metal boride comprises at least one metal selected from the group consisting of molybdenum, ruthenium, niobium, zirconium, rhodium, rhenium, palladium, gold, platinum, nickel, osmium, iridium, titanium, magnesium, calcium and strontium;
the only one layer of the reflecting coating that comprises the mixed metal boride has a thickness of more than 50 nm;
and
the reflecting coating has a reflectivity of at least 60% for EUV radiation.
29. The device of claim 28 , wherein the reflectivity of the reflecting coating is at least 60% for EUV radiation when an angle of incidence of the EUV radiation with the reflecting layer is up to 24.5°.
30. The device of claim 29 , wherein the reflectivity of the reflecting coating is at least 60% for EUV radiation when the angle of incidence of the EUV radiation with the reflecting layer is at least 15°.