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

• US 10,031,423 B2
• Filed: 07/14/2017
• Issued: 07/24/2018
• Est. Priority Date: 07/30/2010
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV), CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: ASML Netherlands BV (ASML Holding NV), CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• 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
• Primary Examiner(s): Iacoletti, Michelle M
• Application Number:
  US15/650,533
• Publication Number:
  US 20170315449A1
• Time in Patent Office: 375 Days
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G02B 17/0647 using more than three curved mirrors G02B17/0668, G02B17/0694 take precedence
• CPC Class Codes: G02B 27/0043 in projection exposure systems, e.g. microlithographic systems
• CPC Class Codes: G02B 3/00 Simple or compound lenses
• CPC Class Codes: G02B 5/00 Optical elements other than lenses light guides G02B6/00; optical logic elements G02F3/00
• CPC Class Codes: G02B 5/08 Mirrors vehicle mirrors involving special optical features B60R1/08
• CPC Class Codes: G02B 5/0816 Multilayer mirrors, i.e. having two or more reflecting layers G02B5/0883, G02B5/0891 take precedence
• CPC Class Codes: G02B 5/0891 Ultraviolet [UV] mirrors apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06
• CPC Class Codes: G02B 7/1815 with cooling or heating systems cooling arrangements for laser mirrors H01S3/0401
• CPC Class Codes: G03B 27/542 for copying cameras, reflex exposure lighting
• CPC Class Codes: G03F 7/7015 Details of optical elements
• CPC Class Codes: G03F 7/702 Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems
• CPC Class Codes: G03F 7/70233 Optical aspects of catoptric systems, i.e. comprising only reflective elements, e.g. extreme ultraviolet [EUV] projection systems
• CPC Class Codes: G03F 7/70316 Details of optical elements, e.g. of Bragg reflectors, extreme ultraviolet [EUV] multilayer or bilayer mirrors or diffractive optical elements
• CPC Class Codes: G03F 7/70825 Mounting of individual elements, e.g. mounts, holders or supports workpiece or mask holders G03F7/707
• CPC Class Codes: G03F 7/70891 Temperature
• CPC Class Codes: G03F 7/70958 Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties
• CPC Class Codes: G21K 1/062 Devices having a multilayer structure
• CPC Class Codes: G21K 2201/061 characterised by a multilayer structure
• CPC Class Codes: G21K 2201/064 having a curved surface

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.

Claims

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 C2, wherein the resistive coating C2 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 C2 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 C2 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 C2 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 C2 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 C2 comprise the same metal.

10. The mirror of claim 1, wherein the resistive coating C2 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.