Microlithographic apparatus

Patent metadata

Field	Value
Publication number	US-9348234-B2
Application number	US-201514845574-A
Country	US
Kind code	B2
Filing date	Sep 4, 2015
Priority date	Mar 13, 2013
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

A projection objective of a microlithographic projection apparatus has a wavefront correction device ( 42 ) comprising a mirror substrate ( 44; 44 a, 44 b ) that has two opposite optical surfaces ( 46, 48 ), through which projection light passes, and a circumferential rim surface ( 50 ) extending between the two optical surfaces ( 46, 48 ). A first and a second optical system (OS 1 , OS 2 ) are configured to direct first and second heating light (HL 1 , HL 2 ) to different portions of the rim surface ( 50 ) such that at least a portion of the first and second heating light enters the mirror substrate ( 44; 44 a, 44 b ). A temperature distribution caused by a partial absorption of the heating light (HL 1 , HL 2 ) results in a refractive index distribution inside the mirror substrate ( 44; 44 a, 44 b ) that corrects a wavefront error. At least the first optical system (OS 1 ) comprises a focusing optical element ( 55 ) that focuses the first heating light in a focal area ( 56 ) such that the first heating light emerging from the focal area ( 56 ) impinges on the rim surface ( 50 ).

First claim

The invention claimed is:

1. An apparatus, comprising:
an illumination system;
a projection objective; and
a wavefront correction device, comprising:
a mirror, comprising:
a mirror substrate having a front surface, a back surface and a circumferential rim surface extending between the front surface of the mirror substrate and the back surface of the mirror substrate; and
a reflective coating supported by the front surface of the mirror substrate, the reflective coating configured to reflect projection light that impinges on the reflective coating;

a first optical system configured to direct first heating light to a first portion of the rim surface so that at least a portion of the first heating light enters the mirror substrate, the first optical system comprising a focusing optical element configured to focus the first heating light in a focal area so that the first heating light that emerges from the focal area impinges on the first portion of the rim surface;
a second optical system is configured to direct second heating light to a second portion of the rim surface so that at least a portion of the second heating light enters the mirror substrate; and
an absorber configured so that, during use of the wavefront correction device, all first and second heating light beams impinge on the absorber after leaving the mirror substrate,

wherein:
the second portion of the rim surface is different from the first portion of the rim surface;
the wavefront correction device is configured so that, during use of the wavefront correction device, partial absorption of the first heating light and the second heating light causes a temperature distribution in the mirror substrate that deforms the mirror to at least partially correct a wavefront error; and
the apparatus is a microlithographic projection exposure apparatus.

2. The apparatus of claim 1 , wherein the first optical system comprises a blind having an aperture, and the focal area is positioned in the aperture.

3. The apparatus of claim 1 , wherein the wavefront correction device is configured so that, during use of the wavefront correction device, after the first heating light enters the mirror substrate, the first heating light propagates through the mirror substrate as collimated light.

4. The apparatus of claim 1 , wherein the rim surface comprises a cylindrical surface or a conical surface.

5. The apparatus of claim 1 , wherein the first portion of the rim surface is curved in a plane intersecting the first portion of the rim surface and containing a symmetry axis of the mirror.

6. The apparatus of claim 1 , wherein the wavefront correction device further comprises:
a light source configured to emit heating light; and
a beam splitter configured so split the heating light emitted by the light source into the first heating light and the second heating light.

7. The apparatus of claim 1 , wherein:
the first optical system comprises a single first light source configured to produce the first heating light; and
the second optical system comprises a single second light source configured to produce the second heating light.

8. The apparatus of claim 1 , wherein the first optical system comprises a spatial light modulator configured to change an intensity of the first heating light in a spatially resolved manner to provide a plurality of first heating light beams, and the spatial light modulator is configured to individually change an intensity of each of the first heating light beams.

9. The apparatus of claim 8 , wherein the spatial light modulator comprises an array of beam deviating elements, and each beam deviating element is configured to deflect impinging first heating light by a deflection angle that is variable in response to a control signal.

10. The apparatus of claim 8 , wherein the spatial light modulator comprises a blind comprising a plurality of apertures, each aperture a size and/or transmissivity that is changeable in response to a control signal.

11. The apparatus of claim 1 , wherein the first optical system comprises a reflective surface configured to reflect at least 70% of heating light which, during use of the wavefront correction device, traverses the mirror substrate so that, upon reflecting at the reflective surface, the heating light again traverses the mirror substrate.

12. The apparatus of claim 11 , wherein the reflective surface is configured so that a direction of the reflected heating light differs from a direction of the light impinging on the reflective surface.

13. The apparatus of claim 12 , wherein the direction of the reflected light differs from the direction of the impinging light by an angle between 180.05° and 185°.

14. The apparatus of claim 1 , wherein, in at least one plane, each of the focusing element and the mirror substrate both has an optical effect of positive lenses.

15. The apparatus of claim 1 , wherein the focal area is a focal point, or the focal area is a focal line.

16. The apparatus of claim 1 , wherein the projection light has a center wavelength between 5 nm and 50 nm.

17. The apparatus of claim 1 , wherein:
the first heating light comprises first heating light beams;
the first optical system comprises first light detectors configured so that, during use of the wavefront correction device, the first light detectors measure irradiance variations of the first heating light beams after the first heating light beams leave the mirror substrate;
the second heating light comprises second heating light beams; and
the second optical system comprises second light detectors configured so that, during use of the wavefront correction device, the second light detectors measure irradiance variations of the second heating light beams after the second light beams leave the mirror substrate.

18. The apparatus of claim 17 , further comprising a control unit configured so that, during use of the wavefront correction device, the control unit controls the first and second optical systems based on the irradiance variations measured by the first and second light detectors.

19. An apparatus, comprising:
an illumination system;
a projection objective; and
a wavefront correction device, comprising:
a mirror, comprising:
a mirror substrate having a front surface, a back surface and a circumferential rim surface extending between the front surface of the mirror substrate and the back surface of the mirror substrate; and
a reflective coating supported by the front surface of the mirror substrate, the reflective coating configured to reflect projection light that impinges on the reflective coating;

a first optical system configured to direct first heating light to a first portion of the rim surface so that at least a portion of the first heating light enters the mirror substrate, the first optical system comprising a focusing optical element configured to focus the first heating light in a focal area so that the first heating light that emerges from the focal area impinges on the first portion of the rim surface; and
a second optical system is configured to direct second heating light to a second portion of the rim surface so that at least a portion of the second heating light enters the mirror substrate;

wherein:
the second portion of the rim surface is different from the first portion of the rim surface;
the wavefront correction device is configured so that, during use of the wavefront correction device, partial absorption of the first heating light and the second heating light causes a temperature distribution in the mirro

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Bittner Boris
• Wabra Norbert
• Schneider Sonja
• Schoemer Ricarda
• Von Hodenberg Martin
• Wagner Hendrik
• Iliew Rumen

Classifications

• G03F7/702

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

• G03F7/70191 Primary

  Optical correction elements, filters or phase plates for controlling intensity, wavelength, polarisation, phase or the like · CPC title

• G03F7/70891 Primary

  Temperature · CPC title