ILLUMINATION SYSTEM OF A MICROLITHOGRAPHIC PROJECTION EXPOSURE APPARATUS

• US 20100165318A1
• Filed: 03/04/2010
• Published: 07/01/2010
• Est. Priority Date: 09/14/2007
• Status: Active Grant

• Current Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: Carl Zeiss AG (Carl-Zeiss-Stiftung)
• Inventors: Walldorf, Daniel, Fiolka, Damian, Saenger, Ingo
• Granted Patent: US 9,316,920 B2
• Time in Patent Office: Days
• US Class Current: 355/71
• CPC Class Codes: G03F 7/70116 Off-axis setting using a programmable means, e.g. liquid crystal display [LCD], digital micromirror device [DMD] or pupil facets
• CPC Class Codes: G03F 7/70191 Optical correction elements, filters or phase plates for controlling intensity, wavelength, polarisation, phase or the like
• 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 7/70566 Polarisation control
• CPC Class Codes: G03F 7/70966 Birefringence

Abstract

The disclosure concerns an illumination system of a microlithographic projection exposure apparatus. The illumination system includes a mirror arrangement which has a plurality of mirror units and at least one element arranged in front of the mirror arrangement in the light propagation direction to produce at least two different states of polarization incident on different mirror units. The mirror units are displaceable independently of each other for altering an angle distribution of the light reflected by the mirror arrangement.

Claims

1. An illumination system, comprising:

a mirror arrangement comprising a plurality of mirror units displaceable independently of each other to alter an angle distribution of light reflected by the mirror arrangement, each mirror unit comprising at least one mirror element; and

at least one element that is in front of the mirror arrangement in a propagation direction of the light so that the at least one element can produce at least two different states of polarization incident on different mirror units and/or different mirror elements,

wherein;

the at least one element comprises a birefringent element configured to split the light into an ordinary and an extraordinary ray;

the ordinary and the extraordinary ray have mutually perpendicular polarization directions;

the ordinary ray and the extraordinary ray can be deflected in different directions by the mirror arrangement; and

the illumination system is configured to be used in a microlithographic projection exposure apparatus.

2. The illumination system as set forth in claim 1, wherein the ordinary ray and the extraordinary ray are incident on different mirror units or different mirror elements.

3. The illumination system as set forth in claim 1, wherein the ordinary ray and the extraordinary ray are incident on mutually adjacent mirror units or on mirror elements of the same mirror unit.

4. The illumination system as set forth in claim 1, wherein the mirror arrangement comprises first mirror units and second mirror units, the first mirror units are optimized for a first polarization direction, and the second mirror units are optimized for a second polarization direction perpendicular to the first polarization direction.

5. The illumination system as set forth in claim 1, further comprising a microlens arrangement comprising a plurality of microlenses, wherein the birefringent element is between the microlens arrangement and the mirror arrangement.

6. The illumination system as set forth in claim 1, further comprising a rotator element configured to rotate the polarization state, wherein the rotator element is upstream and/or downstream of the birefringent element in the light propagation direction.

7. The illumination system as set forth in claim 6, wherein the rotator element comprises a lambda/2-plate.

8. The illumination system as set forth in claim 1, wherein the birefringent element comprises an optically uniaxial crystal material.

9. The illumination system as set forth in claim 1, wherein the birefringent element comprises an optically active material.

10. The illumination system as set forth in claim 1, wherein the illumination system has an optical axis, and the birefringent element has an optical crystal axis that is not oriented in parallel relationship with the optical axis.

11. The illumination system as set forth in claim 1, further comprising an arrangement of at least two channels associated with respectively different regions of the mirror arrangement, wherein, for those channels the polarization state of the light emanating from the respective channel and incident on the mirror arrangement is adjustable independently of each other.

12. The illumination system as set forth in claim 11, wherein the channels each have at least one respective lambda/2-plate, wherein lambda/2-plates of different channels are adjustable independently of each other.

13. The illumination system as set forth in claim 12, wherein the illumination system has an optical axis, and at least one of the lambda/2-plates is arranged rotatably about the optical axis.

14. The illumination system as set forth in claim 1, wherein a lambda/4-plate is between the birefringent element and the mirror arrangement.

15. The illumination system as set forth in claim 14, wherein the illumination system has an optical axis, and the lambda/4-plate is arranged rotatably about the optical axis.

16. The illumination system as set forth in claim 1, wherein the birefringent element has plane-parallel geometry.

17. The illumination system as set forth in claim 1, wherein the birefringent element has a varying thickness profile as measured in the light propagation direction.

18. The illumination system as set forth in claim 1, wherein the birefringent element comprises a prism.

19. The illumination system as set forth in claim 1, wherein the birefringent element has at least substantially wedge-shaped geometry.

20. The illumination system as set forth in claim 1, wherein the birefringent element comprises at least one retarder that produces, for light passing therethrough, an effective retardation which is less than one half of an operation wavelength of light for the illumination system.

21. The illumination system as set forth in claim 20, wherein the position of the retarder is variable in a plane perpendicular to the light propagation direction.

22. The illumination system as set forth in claim 20, wherein the birefringent element comprises at least two retarders.

23. The illumination system as set forth in claim 22, wherein the at least two retarders produce, for light passing therethrough, effective retardations of opposite sign.

24. The illumination system as set forth in claim 1, wherein the birefringent element comprises at least two sub-elements, and the position of the at least two sub-elements with respect to each other is variable.

25. The illumination system as set forth in claim 1, further comprising a polarizer configured to refresh the polarization state.