Optical system, exposure system, and exposure method

• US 20100141921A1
• Filed: 02/05/2010
• Published: 06/10/2010
• Est. Priority Date: 01/27/2004
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Omura, Yasuhiro
• Granted Patent: US 8,339,578 B2
• Time in Patent Office: Days
• US Class Current: 355/71
• CPC Class Codes: G02B 13/143 for use with ultraviolet radiation
• CPC Class Codes: G02B 17/08 Catadioptric systems used in non-imaging applications G02B19/00
• CPC Class Codes: G02B 17/0892 specially adapted for the UV
• CPC Class Codes: G02B 27/28 for polarising used in stereoscopes G02B30/25
• CPC Class Codes: G03F 7/70091 Illumination settings, i.e. intensity distribution in the pupil plane or angular distribution in the field plane; On-axis or off-axis settings, e.g. annular, dipole or quadrupole settings; Partial coherence control, i.e. sigma or numerical aperture [NA]
• 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 7/70566 Polarisation control
• CPC Class Codes: G03F 7/70966 Birefringence

Abstract

An optical system is able to achieve a substantially azimuthal polarization state in a lens aperture while suppressing loss of light quantity, based on a simple configuration. The optical system of the present invention is provided with a birefringent element for achieving a substantially circumferential distribution or a substantially radial distribution as a fast axis distribution in a lens aperture, and an optical rotator located behind the birefringent element and adapted to rotate a polarization state in the lens aperture. The birefringent element has an optically transparent member which is made of a uniaxial crystal material and a crystallographic axis of which is arranged substantially in parallel with an optical axis of the optical system. A light beam of substantially spherical waves in a substantially circular polarization state is incident to the optically transparent member.

Claims

1. An optical system including an optical axis, comprising:

a first optically transparent member which is made of a uniaxial crystal material and a crystallographic axis of which is arranged substantially in parallel with the optical axis;

a second optically transparent member which is made of a uniaxial crystal material and a crystallographic axis of which is arranged substantially in parallel with the optical axis; and

an optical member located in an optical path between the first optically transparent member and the second optically transparent member and including a predetermined power.

2. The optical system according to claim 1,

wherein the first optically transparent member is made of a material selected from rock crystal, magnesium fluoride, and lithium aluminum calcium fluoride, and

wherein the second optically transparent member is made of rock crystal.

3. The optical system according to claim 1,

wherein a beam bundle of substantially spherical waves in a substantially circular polarization state is incident to the first optically transparent member.

4. The optical system according to claim 3,

wherein the first optically transparent member achieves a substantially circumferential distribution or a substantially radial distribution as a fast axis distribution in a lens aperture, and

wherein the second optically transparent member rotates a polarization state in the lens aperture.

5. The optical system according to claim 1,

wherein the optical member including the predetermined power comprises a lens.

6. The optical system according to claim 1,

said optical system including an illumination optical system which illuminates a surface to be illuminated.

7. The optical system according to claim 6,

wherein the first optically transparent member is located near the surface to be illuminated, or at or near a position optically conjugate with the surface to be illuminated, in an optical path of the illumination optical system, and

wherein the optical member including the predetermined power includes an imaging optical system which establishes the position optically conjugate with the surface to be illuminated.

8. The optical system according to claim 7,

wherein the first optically transparent member is located at or near the position optically conjugate with the surface to be illuminated, in the optical path of the illumination optical system, and

wherein the second optically transparent member is located in the imaging optical system in the illumination optical system.

9. The optical system according to claim 7,

wherein the illumination optical system forms a secondary light source including a predetermined optical intensity distribution, on an illumination pupil surface, and

wherein the predetermined optical intensity distribution of the secondary light source is so set that an optical intensity in a pupil center region being a region on the illumination pupil and including the optical axis is smaller than an optical intensity in a region around the pupil center region.

10. The optical system according to claim 9,

wherein the predetermined optical intensity distribution of the secondary light source includes an optical intensity distribution of an annular shape or multi-pole shape.

11. The optical system according to claim 1,

said optical system being an optical system for lithography.

12. An optical system having an optical axis, comprising:

a first optically transparent member which is made of a uniaxial crystal material and a crystallographic axis of which is arranged substantially in parallel with the optical axis, the first optically transparent member being arranged at a first position; and

a second optically transparent member which is at a position different from the first position in a direction of the optical axis and is made of uniaxial crystal and a crystallographic axis of which is arranged substantially in parallel with the optical axis.

13. The optical system according to claim 12, wherein the first optically transparent member is made of material selected from rock crystal and MgF₂ or LiCaAlF₆;

and

the second optically transparent member is made of rock crystal.

14. The optical system according to claim 13, further comprising an optical member arranged in an optical path between the first optically transparent member and the second optically transparent member and having a predetermined power.

15. The optical system according to claim 14, wherein the optical member with the predetermined power comprises a lens.

16. The optical system according to claim 14, wherein the optical system comprises an illumination optical system for illuminating a plane to be illuminated.

17. The optical system according to claim 16 wherein

the first optically transparent member is arranged at a position adjacent to the plane to be illuminated or at a position optically conjugate with the plane to be illuminated or adjacent thereto, in an optical path of the illumination optical system;

and

the optical member with the predetermined power comprises an imaging optical system for forming a position optically conjugate with the plane to be illuminated.

18. The optical system according to claim 17, wherein

the first optically transparent member is arranged at a position optically conjugate with the plane to be illuminated or adjacent thereto, in an optical path of the illumination optical system;

and

the second optically transparent member is arranged within the imaging optical system located in the illumination optical system.

19. The optical system according to claim 17, wherein

the illumination optical system forms a secondary light source having a predetermined optical intensity distribution, on an illumination pupil plane;

and

the predetermined optical intensity distribution of the secondary light source is so set that an optical intensity in a pupil center region being a region on the illumination pupil and including an optical axis smaller than an optical intensity in a region around the pupil center region.

20. The optical system according to claim 19, wherein the predetermined optical intensity distribution of the secondary light source has an optical intensity distribution of an annular shape or multi-pole shape.

21. The optical system according to claim 12, wherein the optical system is an optical system for lithography.

22. The optical system according to claim 12, wherein a beam bundle of substantially spherical waves in a substantially circular polarization state is incident to the first optically transparent member.

23. The optical system according to claim 12, wherein the first optically transparent member achieves a substantially circumferential distribution or a substantially radial distribution as a fast axis distribution in a lens aperture;

and

the second optically transparent member rotates a polarization state of the lens aperture.

24. The optical system according to claim 23, further comprising an optical member arranged in an optical path between the first optically transparent member and the second optically transparent member and having a predetermined power.

25. The optical system according to claim 24, wherein the optical member with the predetermined power comprises a lens.

26. The optical system according to claim 24, wherein the optical system comprises an illumination optical system for illuminating a plane to be illuminated.

27. The optical system according to claim 26, wherein

the first optically transparent member is arranged at a position adjacent to the plane to be illuminated or at a position optically conjugate with the plane to be illuminated or adjacent thereto, in an optical path of the illumination optical system;

and

the optical member with the predetermined power comprises an imaging optical system for forming a position optically conjugate with the plane to be illuminated.

28. The optical system according to claim 26, wherein

the first optically transparent member is arranged at a position optically conjugate with the plane to be illuminated or adjacent thereto, in an optical path of the illumination optical system;

and

the second optically transparent member is arranged within the imaging optical system located in the illumination optical system.

29. The optical system according to claim 26, wherein

the illumination optical system forms a secondary light source having a predetermined optical intensity distribution, on an illumination pupil plane;

and

the predetermined optical intensity distribution of the secondary light source is so set that an optical intensity in a pupil center region being a region on the illumination pupil and including an optical axis smaller than an optical intensity in a region around the pupil center region.

30. The optical system according to claim 29, wherein the predetermined optical intensity distribution of the secondary light source has an optical intensity distribution of an annular shape or multi-pole shape.

31. The optical system according to claim 12, wherein

the first position is located in a first plane crossing the optical axis;

and

the second position is located in a second plane different from the first plane and crossing the optical axis.

32. The optical system according to claim 12, wherein

the first optically transparent member is arranged so as to include the optical axis;

and

the second optically transparent member is arranged so as to include the optical axis.

33. The optical system according to claim 12, wherein

the optical system comprises an illumination optical system for illuminating a plane to be illuminated, and

the first and second transparent members are included in the illumination optical system.