Mirror, in particular for a microlithographic projection exposure apparatus

Patent metadata

Field	Value
Publication number	US-9810993-B2
Application number	US-201615144982-A
Country	US
Kind code	B2
Filing date	May 3, 2016
Priority date	Nov 4, 2013
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

A mirror, in particular for a microlithographic projection exposure apparatus, has an optically effective surface ( 10 a ), a mirror substrate ( 11 ) and a reflection layer stack ( 12 ) configured to reflect electromagnetic radiation that is incident on the optically effective surface. A metallic diffusion barrier layer ( 13 ) is arranged on that side of the reflection layer stack which faces toward the optically effective surface, and a stabilization layer ( 14 ) is arranged on the side of the diffusion barrier layer that faces toward the optically effective surface ( 10 a ). The stabilization layer reduces deformation of the diffusion barrier layer compared to an analogous structure without such a stabilization layer upon irradiation of the optically effective surface with electromagnetic radiation. The stabilization layer has a porosity, a relative density of which is no more than 80%, where the relative density is defined as the ratio between geometric density and true density.

First claim

What is claimed is:

1. A mirror having an optically effective surface, comprising
a mirror substrate;
a reflection layer stack configured to reflect electromagnetic radiation that is incident on the optically effective surface;
a metallic diffusion barrier layer arranged on a side of the reflection layer stack that faces toward the optically effective surface; and
a stabilization layer arranged on a side of the diffusion barrier layer that faces toward the optically effective surface,
wherein the stabilization layer reduces deformation of the diffusion barrier layer compared to an analogous mirror structure of the mirror without such a stabilization layer upon irradiation of the optically effective surface with electromagnetic radiation; and
wherein the stabilization layer has a porosity with a relative density, which is defined as a ratio between geometric density and true density, of at most 80% and is configured to decrease the absorption of electromagnetic radiation by the stabilization layer compared to an analogous layer structure having a higher true density.

2. The mirror as claimed in claim 1 , wherein the relative density, which is defined as the ratio between geometric density and true density, for the stabilization layer is at most 70%.

3. The mirror as claimed in claim 1 , wherein the stabilization layer comprises at least one material selected from the group consisting of silicon (Si), molybdenum (Mo), boron (B), carbon (C), ruthenium (Ru), rhodium (Rh), and nitrides.

4. The mirror as claimed in claim 1 , wherein the stabilization layer comprises a carbide.

5. The mirror as claimed in claim 4 , wherein the stabilization layer comprises silicon carbide (SiC) or boron carbide (B 4 C).

6. The mirror as claimed in claim 1 , wherein the stabilization layer comprises a nitride.

7. The mirror as claimed in claim 1 , wherein the stabilization layer is formed from atoms bonded in a covalent bond.

8. The mirror as claimed in claim 1 , wherein the stabilization layer has a thickness of at most 4 nm.

9. The mirror as claimed in claim 8 , wherein the stabilization layer has a thickness of at most 2 nm.

10. The mirror as claimed in claim 1 , wherein the diffusion barrier layer comprises at least one material selected from the group consisting of ruthenium (Ru), rhodium (Rh), niobium (Nb), zirconium (Zr), platinum (Pt), iridium (Ir) and silver (Ag).

11. The mirror as claimed in claim 1 , wherein the diffusion barrier layer has a thickness in the range of 0.3 nm to 2 nm.

12. The mirror as claimed in claim 11 , wherein the diffusion barrier layer has a thickness in the range of 0.3 nm to 1.5 nm.

13. The mirror as claimed in claim 1 , configured for an operating wavelength of less than 30 nm.

14. The mirror as claimed in claim 13 , configured for an operating wavelength of less than 15 nm.

15. The mirror as claimed in claim 1 and configured as a mirror of a microlithographic projection exposure apparatus.

16. An optical system of a microlithographic projection exposure apparatus comprising at least one mirror as claimed in claim 1 .

17. The optical system as claimed in claim 16 , configured as an illumination device or as a projection lens.

18. A microlithographic projection exposure apparatus comprising an optical system as claimed in claim 16 .

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Huber Peter

Classifications

• G03F7/702 Primary

  Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems · CPC title

• G21K2201/067

  Construction details · CPC title

• C23C8/20

  Carburising · CPC title

• G21K1/062

  Devices having a multilayer structure · CPC title

• G02B5/0891

  Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06) · CPC title