Method and arrangement for determining the heating condition of a mirror in an optical system

Patent metadata

Field	Value
Publication number	US-10161808-B2
Application number	US-201313863595-A
Country	US
Kind code	B2
Filing date	Apr 16, 2013
Priority date	Nov 25, 2010
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

The invention concerns a method of and an arrangement for determining the heating condition of a mirror in an optical system, in particular in a microlithographic projection exposure apparatus. In an embodiment the mirror is an EUV mirror and a method according to the invention comprises the following steps: deflecting at least one input measuring beam on to the mirror; ascertaining at least one optical parameter of at least one output measuring beam produced from the input measuring beam after interaction with the mirror; and determining the heating condition of the mirror on the basis of the parameter.

First claim

The invention claimed is:

1. A method, comprising:
producing an output beam by interacting an input beam with a substrate of an EUV mirror in a microlithographic projection exposure apparatus without interacting the input beam with an EUV reflective surface of the EUV mirror, the substrate of the EUV mirror supporting the EUV reflective surface of the EUV mirror;
determining an optical parameter of the output beam; and
determining a heating condition of the EUV mirror based on the optical parameter.

2. The method of claim 1 , wherein the substrate of the EUV mirror comprises a material having a refractive index, and the optical parameter depends on the refractive index of the material.

3. The method of claim 1 , wherein the optical parameter comprises an optical path length change.

4. The method of claim 1 , wherein the optical parameter comprises a polarization of the output beam.

5. The method of claim 1 , wherein interacting the input beam with the substrate of the EUV mirror comprises interacting a plurality of input beams with the substrate the EUV mirror.

6. The method of claim 1 , wherein interacting the input beam with the substrate of the EUV mirror comprises interacting a plurality of input beams with the substrate of the EUV mirror at different azimuth angles with respect to an optical axis of the optical system.

7. The method of claim 1 , wherein producing the output beam comprises passing the input beam through the substrate of the EUV mirror at least once.

8. The method of claim 1 , wherein producing the output beam comprises passing the input beam through the substrate of the EUV mirror a plurality of times.

9. The method of claim 1 , wherein the output beam comprises infrared radiation.

10. The method of claim 1 , wherein the optical parameter is interferometrically determined.

11. The method of claim 1 , comprising operating the microlithographic projection exposure apparatus while interacting the input beam with the substrate of the EUV mirror and determining the optical parameter.

12. A method, comprising:
producing an output beam by passing an input beam at least once through a region between a reflecting surface of an EUV mirror and a rear side of the EUV mirror without the input beam impinging on the reflecting surface of the EUV mirror, the EUV mirror being in a microlithographic projection exposure apparatus;
determining an optical parameter of the output beam; and
determining a heating condition of the EUV mirror based on the optical parameter.

13. The method of claim 12 , wherein producing the output beam comprises passing the input beam through the EUV mirror a plurality of times.

14. The method of claim 12 , wherein the region of the EUV mirror comprises a material having a refractive index, and the optical parameter depends on the refractive index of the material.

15. The method of claim 12 , wherein the optical parameter comprises an optical path length change.

16. The method of claim 12 , wherein the optical parameter comprises a polarization of the output beam.

17. The method of claim 12 , wherein passing the input beam through the region of the EUV mirror comprises passing a plurality of input beams through the region of the EUV mirror.

18. The method of claim 12 , wherein passing the input beam through the region of the EUV mirror comprises passing a plurality of input beams through the region of the EUV mirror at different azimuth angles with respect to an optical axis of the optical system.

19. The method of claim 12 , wherein passing the input beam through the region of the EUV mirror at least once comprises passing the input beam through the region of the EUV mirror twice.

20. The method of claim 12 , wherein passing the input beam through the region of the EUV mirror at least once comprises passing the input beam through the region of the EUV mirror a plurality of times.

21. The method of claim 12 , wherein the optical parameter is interferometrically determined.

22. The method of claim 12 , comprising operating the microlithographic projection exposure apparatus while interacting the input beam with the substrate of the EUV mirror and determining the optical parameter.

23. The method of claim 12 , wherein the output beam comprises infrared radiation.

24. A method, comprising:
producing an output beam by reflecting an input beam off an optical element supported by a mirror in a microlithographic projection exposure apparatus without the input beam impinging on an EUV reflective surface of the mirror;
determining an optical parameter of the output beam; and
determining a heating condition of the mirror based on the optical parameter.

25. The method of claim 24 , wherein the optical element comprises a distributed Bragg reflector.

26. The method of claim 25 , further comprising determining a reflectivity of the distributed Bragg reflector at a predetermined wavelength.

27. The method of claim 24 , wherein the output beam comprises infrared radiation.

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Vogt Peter
• Hermann Martin
• Dier Oliver
• Major Andras G

Classifications

• G01B9/02081

  simultaneous quadrature detection, e.g. by spatial phase shifting · CPC title

• G02B7/181

  with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation · CPC title

• G03F7/70891

  Temperature · CPC title

• G01M11/005

  Testing of reflective surfaces, e.g. mirrors · CPC title

• G01B2290/70

  Using polarization in the interferometer · CPC title