EUV exposure apparatus with reflective elements having reduced influence of temperature variation

Patent metadata

Field	Value
Publication number	US-10031423-B2
Application number	US-201715650533-A
Country	US
Kind code	B2
Filing date	Jul 14, 2017
Priority date	Jul 30, 2010
Publication date	Jul 24, 2018
Grant date	Jul 24, 2018

Abstract

A projection lens of an EUV-lithographic projection exposure system with at least two reflective optical elements each comprising a body and a reflective surface for projecting an object field on a reticle onto an image field on a substrate if the projection lens is exposed with an exposure power of EUV light, wherein the bodies of at least two reflective optical elements comprise a material with a temperature dependent coefficient of thermal expansion which is zero at respective zero cross temperatures, and wherein the absolute value of the difference between the zero cross temperatures is more than 6K.

First claim

What is claimed is:

1. A mirror comprising:
a body MB k having a reflective surface MS k ;
a material with a temperature dependent coefficient of thermal expansion which is zero at a zero cross temperature T 0k ;
said body MB k is at least partly coated with a resistive coating C 2 , wherein the resistive coating C 2 has an electrical resistance suitable to heat the body by electrical resistive heating;
said mirror being adapted for a projection lens of an EUV-lithographic projection exposure system for projecting an object field on a reticle onto an image field on a substrate if the projection lens is exposed with an exposure power of EUV light with a wavelength in a wavelength range of less than 50 nm; and,
wherein the coating C 2 covers at least part of the mirror body MB k on at least one surface that does not comprise the area of the reflective surface MS k .

2. The mirror of claim 1 , wherein the resistive heating is between 0.01 W and 1 W.

3. The mirror of claim 1 , wherein the coating C 2 is connected to a voltage source VS selected from the group consisting of a voltage source attached to the mirror body MB k and a voltage source electrically connecting the mirror body MB k by a wire.

4. The mirror of claim 1 , wherein the body MB k of the optical element M k is semitransparent to an IR radiation and wherein the resistive coating C 2 is on a reflective coating C coated on the entire surface of the body MB k or on almost the entire surface of the body MB k , wherein the reflective coating C reflects IR radiation inside the body MB k .

5. The mirror of claim 4 , wherein the body MB k comprises a surface area not coated with the coatings C and C 2 or a surface area with a coating being semitransparent to the IR radiation, for coupling in an IR radiation into the body MB k .

6. The mirror of claim 5 , wherein the surface area is arranged on the side of the body MB k with the reflective surface MS k .

7. The mirror of claim 6 , wherein the surface area surrounds the reflective surface MS k .

8. The mirror of claim 5 , wherein the surface area comprises a surface roughness to scatter an IR radiation into the body, or the surface area comprises a diffractive structure to distribute an IR radiation within the body MB k by diffraction.

9. The mirror of claim 4 , wherein the reflective coating C and the resistive coating C 2 comprise the same metal.

10. The mirror of claim 1 , wherein the resistive coating C 2 comprises a metal.

11. A mirror comprising
a body MB k and a reflective surface MS k ;
the body MB k comprising a material with a temperature dependent coefficient of thermal expansion which is zero at a zero cross temperature wherein at least a part of the surface of the body MB k comprises a wire grid for electrically resistive heating of the body MB k ;
the mirror being adapted for a projection lens of an EUV-lithographic projection exposure system for projecting an object field on a reticle onto an image field on a substrate if the projection lens is exposed with an exposure power of EUV light with a wavelength in a wavelength range of less than 50 nm; and,
the wire grid being formed by a resistive coating with a coating material by etching pattern structures into the resistive coating.

12. The mirror of claim 11 , wherein the coating material is selected from the group consisting of metal, semiconductor material, a material comprising carbon and invar.

13. The mirror of claim 11 , wherein the wire grid comprises a pattern structure with at least N >1electrical circuits, and the pattern structure comprises at least N+1 electrical connectors to connect the N electrical circuits to an electrical power source to subject the N electrical circuits with an electrical power, being independently controlled from each other.

14. The mirror of claim 13 , wherein the pattern structure of the wire grid is covered by an insulating layer, comprising a low CTE material.

15. The mirror of claim 14 , wherein the insulating layer is polished, having surface figure data within an accuracy of ±3 nm RMS as required for the reflective surface MS k of the mirror.

16. The mirror of claim 15 , wherein the reflective surface MS k comprises a multilayer stack being arranged above the insulating layer, or being arranged above a compaction layer arranged above the insulating layer.

17. The mirror of claim 11 , wherein the wire grid is connected to an electrical power source selected from the group consisting of an electrical power source attached to the mirror body MB k and an electrical power source electrically connecting the mirror body MB k by a wire.

18. The mirror of claim 17 , wherein the electrical power source comprises at least two voltage and/or current sources or a multiplexer circuit.

19. The mirror of claim 11 , wherein the wire grid covers more than 50% of the area of the reflective surface MSk .

20. The mirror of claim 11 , wherein:
the wire grid defines a wire grid structure; and,
the wire grid includes wires having an electrical resistance which is measured to measure the temperature with a spatial resolution which is defined by the wire grid structure.

Assignees

• Zeiss Carl Smt Gmbh
• Asml Netherlands Bv

Inventors

• Baer Norman
• Loering Ulrich
• Natt Oliver
• Wittich Gero
• Laufer Timo
• Kuerz Peter
• Limbach Guido
• Hembacher Stefan
• Walter Holger
• Kwan Yim-Bun-Patrick
• Hauf Markus
• Stickel Franz-Josef
• Van Schoot Jan

Classifications

• G03B27/542

  for copying cameras, reflex exposure lighting · CPC title

• G02B17/0647

  using more than three curved mirrors (G02B17/0668, G02B17/0694 take precedence) · CPC title

• G02B5/08

  Mirrors {(vehicle mirrors involving special optical features B60R1/08)} · CPC title

• G02B3/00

  Simple or compound lenses · CPC title

• B82Y10/00 Primary

  Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic · CPC title