Optical arrangement for EUV lithography and method for configuring such an optical arrangement

Patent metadata

Field	Value
Publication number	US-9263161-B2
Application number	US-201213618824-A
Country	US
Kind code	B2
Filing date	Sep 14, 2012
Priority date	Oct 28, 2011
Publication date	Feb 16, 2016
Grant date	Feb 16, 2016

Abstract

An optical arrangement, e.g. projection lens, for EUV lithography, provided with: a first optical element ( 22 ) having a reflective surface ( 31 a ) and a first substrate ( 32 ) composed of TiO 2 -doped quartz glass, which has a temperature-dependent coefficient of thermal expansion having a zero crossing at a first zero crossing temperature (T ZC1 ), and a second optical element ( 24 ) having a reflective surface ( 36 a ) and a second substrate ( 37 ) composed of TiO 2 -doped quartz glass, which has a temperature-dependent coefficient of thermal expansion having a zero crossing at a second zero crossing temperature (T ZC2 ), which is different from the first. A gradient of the coefficient of thermal expansion of the first substrate ( 32 ) at the first zero crossing temperature (T ZC1 ) and/or a gradient of the coefficient of thermal expansion of the second substrate ( 37 ) at the second zero crossing temperature (T ZC2 ) have/has a negative sign.

First claim

What is claimed is:

1. Optical arrangement for extreme-ultraviolet (EUV) lithography, comprising:
a first optical element, which comprises a reflective surface and a first substrate composed of TiO 2 -doped quartz glass, which has a temperature-dependent coefficient of thermal expansion having a zero crossing at a first zero crossing temperature (T ZC1 ), and
a second optical element, which comprises a reflective surface and a second substrate composed of TiO 2 -doped quartz glass, which has a temperature-dependent coefficient of thermal expansion having a zero crossing at a second zero crossing temperature (T ZC2 ), which is different from the first, wherein at least one of:
a gradient (ΔCTE 1 ) of the coefficient of thermal expansion of the first substrate at the first zero crossing temperature (T ZC1 ) and a gradient (ΔCTE 2 ) of the coefficient of thermal expansion of the second substrate at the second zero crossing temperature (T ZC2 ) has a negative sign.

2. Optical arrangement according to claim 1 , wherein the gradient (ΔCTE 1 ) of the coefficient of thermal expansion of the first substrate at the first zero crossing temperature (T ZC1 ) and the gradient (ΔCTE 2 ) of the coefficient of thermal expansion of the second substrate at the second zero crossing temperature (T ZC2 ) differ in terms of sign.

3. Optical arrangement according to claim 1 , wherein at least one of: the absolute value of the gradient (ΔCTE 1 ) of the coefficient of thermal expansion of the first substrate at the first zero crossing temperature (T ZC1 ) and the absolute value of the gradient (ΔCTE 2 ) of the coefficient of thermal expansion of the second substrate at the second zero crossing temperature (T ZC2 ) is less than 1.0 ppb/K 2 .

4. Optical arrangement according to claim 1 , wherein the absolute value of the difference (|T ZC2 −T ZC1 |) between the first zero crossing temperature (T ZC1 ) and the second zero crossing temperature (T ZC2 ) is more than 6 K.

5. Optical arrangement according to claim 1 , wherein the TiO 2 content of the first substrate differs from the TiO 2 content of the second substrate.

6. Optical arrangement according to claim 1 , wherein the first substrate has a TiO 2 content of between 8% and 12%.

7. Optical arrangement according to claim 1 , wherein the second substrate has a TiO 2 content of more than 12%.

8. Optical arrangement according to claim 1 , wherein both the first and the second zero crossing temperature (T ZC1 , T ZC2 ) lie in a temperature range of between 0° C. and 100° C.

9. Optical arrangement according to claim 1 , wherein a reflective coating is applied to at least one of: the first and the second substrate, the reflective surface being formed at the reflective coating.

10. Optical arrangement according to claim 9 , wherein at least one functional layer is fitted between at least one of: the first and the second substrate and the reflective coating.

11. Optical arrangement according to claim 1 , further comprising:
at least one heating device for heating at least one substrate,
and a control device for driving the at least one heating device to set the temperature of the at least one substrate to a working temperature (T A1 ).

12. Optical arrangement according to claim 11 , wherein the working temperature (T A1 ) deviates from the zero crossing temperature (T ZC1 ) of the substrate by less than 3 K.

13. Method for configuring an optical arrangement for extreme ultraviolet (EUV) lithography, wherein the optical arrangement comprises at least two optical elements having a surface that reflects EUV radiation, and having a substrate composed of TiO 2 -doped quartz glass, the method comprising:
selecting a substrate for the optical elements from a first or a second group of substrates composed of TiO 2 -doped quartz glass, wherein the first group has a temperature-dependent coefficient of thermal expansion having a zero crossing at a first zero crossing temperature (T ZC1,O ), wherein the second group has a coefficient of thermal expansion having a zero crossing at a second zero crossing temperature (T ZC2,O ), which is different from the first, and wherein at least one of: a gradient (ΔCTE 1,O ), of the coefficient of thermal expansion of the first group of substrates at the first zero crossing temperature (T ZC1,O ) and a gradient (ΔCTE 2,O ) of the coefficient of thermal expansion of the second group of substrates at the second zero crossing temperature (T ZC2,O ) has a negative sign.

14. Method according to claim 13 , wherein selecting is effected in a manner dependent on the position of a respective optical element in the optical arrangement.

15. Method according to claim 13 , wherein the first group of substrates at the first zero crossing temperature (T ZC1,O ) has a gradient (ΔCTE 1,O ) of the coefficient of thermal expansion whose sign differs from the gradient (ΔCTE 2,O ) of the coefficient of thermal expansion of the second group of substrates at the second zero crossing temperature (T ZC2,O ).

16. Method according to claim 13 , wherein the TiO 2 content of the first group of substrate materials differs from the TiO 2 content of the second group of substrate materials.

17. Method according to claim 13 , further comprising:
performing a heat treatment of the selected substrate for at least one of: changing the zero crossing temperature (T ZC1,O , T ZC2,O ) to a desired zero crossing temperature (T ZC1 , T ZC2 ) for the optical element and reducing the gradient (ΔCTE 1,O , ΔCTE 2,O ) of the coefficient of thermal expansion to an absolute value of less than 1.0 ppb/K 2 at the desired zero crossing temperature (T ZC1 , T ZC2 ) of the optical element.

18. Method according to claim 17 , wherein the heat treatment comprises:
heating the selected substrate to a holding temperature of at least 900° C., holding the substrate at the holding temperature for at least 40 hours, and cooling the substrate at a cooling rate of between 0.1 K/h and 2.0 K/h in a temperature range between the holding temperature and 500° C.

Assignees

• Clauss Wilfried
• Zeiss Carl Smt Gmbh

Inventors

• Clauss Wilfried

Classifications

• G02B17/0657

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• G02B7/008

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

• B82Y10/00

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

• G21K2201/067

  Construction details · CPC title

• G21K1/062 Primary

  Devices having a multilayer structure · CPC title