POLARIZATION CONVERTING UNIT, ILLUMINATION OPTICAL SYSTEM, EXPOSURE APPARATUS, AND DEVICE MANUFACTURING METHOD

• US 20110037962A1
• Filed: 06/23/2010
• Published: 02/17/2011
• Est. Priority Date: 08/17/2009
• Status: Abandoned Application

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: TANITSU, Osamu
• Application Number:
  US12/821,742
• Publication Number:
  US 20110037962A1
• Time in Patent Office: Days
• US Class Current: 355/67
• CPC Class Codes: G02B 27/286 for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34
• CPC Class Codes: G03F 7/70566 Polarisation control

Abstract

According to one embodiment, a polarization converting unit configured to convert incident light into light in a predetermined polarization state has a first optical element and a second optical element. The first optical element has a plurality of first regions, and at least two adjacent first regions have respective different thicknesses so as to have different polarization conversion properties. Likewise, the second optical element also has a plurality of second regions, and at least two adjacent second regions have different polarization conversion properties. The first and second optical elements are arranged so that a light beam having passed through one first region is incident to two adjacent second regions, whereby the sum of thicknesses of the first and second optical elements is varied depending upon a passing position of light.

Claims

1. A polarization converting unit arranged on an optical axis of an optical system and configured to convert a polarization state of propagation light passing along an optical-axis direction corresponding to the optical axis, the polarization converting unit comprising:

a first optical element comprised of an optical material with an optical rotatory power, which is arranged so as to have a crystal axis coincident or parallel with the optical-axis direction, the first optical element having a plurality of first regions with respective polarization conversion properties to rotate linearly polarized light incident thereto as the propagation light, around the optical-axis direction; and

a second optical element comprised of an optical material with an optical rotatory power, which is arranged on the exit side of the first optical element and which is arranged so as to have a crystal axis coincident or parallel with the optical-axis direction, the second optical element having a plurality of second regions with respective polarization conversion properties to rotate linearly polarized light incident thereto as the propagation light, around the optical-axis direction,

wherein at least two first regions selected from the plurality of first regions have their respective thicknesses different from each other in the optical-axis direction, and wherein the plurality of first regions are arranged so that two first regions with mutually different polarization conversion properties are adjacent to each other,

wherein at least two second regions selected from the plurality of second regions have their respective thicknesses different from each other in the optical-axis direction, and wherein the plurality of second regions are arranged so that two second regions with mutually different polarization conversion properties are adjacent to each other, and

wherein the first and second optical elements are arranged so that a light beam having passed through one first region of the first optical element is incident to two adjacent second regions of the second optical element, whereby the sum of respective thicknesses in the optical-axis direction of first and second regions through which a first reference axis parallel to the optical-axis direction passes is different from the sum of respective thicknesses in the optical-axis direction of other first and second regions through which a second reference axis parallel to the optical-axis direction and different from the first reference axis passes.

2. A polarization converting unit according to claim 1, wherein the plurality of first regions of the first optical element are arrayed so as to surround the optical axis along a circumferential direction corresponding to a direction of rotation around the optical axis on a plane perpendicular to the optical axis, and the plurality of second regions of the second optical element are arrayed so as to surround the optical axis along the circumferential direction around the optical axis.

3. A polarization converting unit according to claim 2, wherein the plurality of first regions of the first optical element are regions obtained by equally dividing the optical material of a circular or annular shape along the circumferential direction of the optical material,

wherein the plurality of second regions of the second optical element are regions obtained by equally dividing the optical material of a circular or annular shape along the circumferential direction of the optical material, and

wherein, when each of the first and second optical elements is viewed along the optical-axis direction from the entrance side of the first optical element, the first and second optical elements are arranged so that a boundary line between two adjacent first regions out of the plurality of first regions is optically correspondent to a center line connecting a center of an entrance surface of a corresponding second region out of the plurality of second regions, and the optical axis.

4. A polarization converting unit according to claim 1, wherein the first optical element has a plurality of optically rotatory members of a plane-parallel plate shape comprised of an optical material with an optical rotatory power, as the plurality of first regions.

5. A polarization converting unit according to claim 1, wherein the first optical element has a plurality of wave plates to convert incident light into light in a predetermined polarization state, as the plurality of first regions.

6. A polarization converting unit according to claim 1, wherein the first optical element has a plurality of polarizers to selectively transmit a light component in a predetermined polarization state from incident light, as the plurality of first regions.

7. A polarization converting unit according to claim 1, wherein the second optical element has a plurality of optically rotatory members of a plane-parallel plate shape comprised of an optical material with an optical rotatory power, as the plurality of second regions.

8. A polarization converting unit according to claim 1, wherein the second optical element has a plurality of wave plates to convert incident light into light in a predetermined polarization state, as the plurality of second regions.

9. A polarization converting unit according to claim 1, wherein the first and second optical elements are arranged in a state in which they are adjacent to each other along the optical-axis direction.

10. A polarization converting unit according to claim 1, further comprising a relay optical system arranged between the first optical element and the second optical element and making the first optical element and the second optical element optically conjugate with each other.

11. A polarization converting unit according to claim 1, the polarization converting unit being arranged in an optical path of an illumination optical system configured to illuminate an illumination target surface with light from a light source, and at or near an illumination pupil of the illumination optical system.

12. An illumination optical system configured to illuminate an illumination target surface with light from a light source, the illumination optical system comprising a polarization converting unit according to claim 1, which is arranged in an optical path between the light source and the illumination target surface.

13. An illumination optical system according to claim 12, wherein the polarization converting unit is arranged at or near an illumination pupil of the illumination optical system.

14. An illumination optical system according to claim 13, the illumination optical system being used in combination with a projection optical system for forming a plane optically conjugate with the illumination target surface, wherein the illumination pupil is arranged at a position optically conjugate with an aperture stop of the projection optical system.

15. An exposure apparatus configured to expose a photosensitive substrate to transfer a predetermined pattern thereto, the exposure apparatus comprising an illumination optical system according to claim 12 configured to illuminate the predetermined pattern.

16. An exposure apparatus according to claim 15, further comprising a projection optical system configured to form an image of the predetermined pattern on the photosensitive substrate.

17. A device manufacturing method, comprising:

exposing a photosensitive substrate to transfer a predetermined pattern thereto, using an exposure apparatus according to claim 15;

developing the photosensitive substrate to which the predetermined pattern is transferred, thereby to form a mask layer in a shape corresponding to the predetermined pattern on a surface of the photosensitive substrate; and

processing the surface of the photosensitive substrate through the mask layer.

18. A polarization converting unit arranged on an optical axis of an optical system and configured to convert a polarization state of propagation light passing along an optical-axis direction corresponding to the optical axis, the polarization converting unit comprising:

a first optically rotatory member to rotate linearly polarized light incident thereto as the propagation light, around the optical-axis direction, the first optically rotatory member being comprised of an optical material with an optical rotatory power, which is arranged so as to have a crystal axis coincident or parallel with the optical-axis direction, and having a first thickness distribution of thicknesses in the optical-axis direction different at a plurality of locations; and

a second optically rotatory member to rotate linearly polarized light incident as the propagation light thereto through the first optically rotatory member, around the optical-axis direction, the second optically rotatory member being comprised of an optical material with an optical rotatory power, which is arranged so as to have a crystal axis coincident or parallel with the optical-axis direction, and having a second thickness distribution of thicknesses in the optical-axis direction different at a plurality of locations,

wherein the first and second optically rotatory members are arranged so that the sum of respective thicknesses in the optical-axis direction at predetermined locations in the first and second optically rotatory members through which a first reference axis parallel to the optical-axis direction passes is different from the sum of respective thicknesses in the optical-axis direction at other locations in the first and second optically rotatory members through which a second reference axis parallel to the optical-axis direction and different from the first reference axis passes.

19. A polarization converting unit according to claim 18, wherein at least one of the first and second optically rotatory members is composed of a single member having a continuous surface.

20. A polarization converting unit according to claim 18, wherein at least one of the first and second optically rotatory members is composed of a single first divided member having a continuous surface and a single second divided member having a continuous surface.

21. A polarization converting unit according to claim 18, wherein at least one of the first and second optically rotatory members is surface-processed by etching at least one surface of a plane-parallel plate.

22. A polarization converting unit according to claim 18, wherein the first and second optically rotatory members are arranged so as to intersect with the optical axis, and at least one of the first and second optically rotatory members has thicknesses in the optical-axis direction varying along a circumferential direction corresponding to a direction of rotation around the optical axis on a plane perpendicular to the optical axis.

23. A polarization converting unit according to claim 18, wherein the first and second optically rotatory members are arranged so as to intersect with the optical axis, and at least one of the first and second optically rotatory members is composed of a plurality of regions divided in a circumferential direction corresponding to a direction of rotation around the optical axis on a plane perpendicular to the optical axis, the plurality of regions being arranged so that two regions having respective thicknesses different in the optical-axis direction are adjacent to each other.

24. A polarization converting unit according to claim 23, wherein each of the plurality of regions has a contour obtained by dividing the optical material of a circular or annular shape along a circumferential direction of the optical material.

25. A polarization converting unit according to claim 18, wherein the first and second optically rotatory members have the same structure.

26. A polarization converting unit according to claim 25, wherein, when the first and second optically rotatory members are viewed along the optical-axis direction, the first and second optically rotatory members are arranged so that the first thickness distribution is coincident with the second thickness distribution.

27. A polarization converting unit according to claim 18, wherein at least one of the first and second optically rotatory members is comprised of quartz crystal.

28. A polarization converting unit according to claim 18, wherein the first and second optically rotatory members are arranged in a state in which they are adjacent to each other along the optical-axis direction.

29. A polarization converting unit according to claim 18, the polarization converting unit being arranged in an optical path of an illumination optical system for illuminating an illumination target surface with light from a light source, and in a pupil space including an illumination pupil of the illumination optical system.

30. A polarization converting unit according to claim 18, wherein each of the first and second thickness distributions is a distribution in which, along with position information of portions in the optical material, thicknesses in the optical-axis direction of the respective portions are made correspondent on a plane perpendicular to the optical-axis direction, and nonuniform distribution.

31. An illumination optical system configured to illuminate an illumination target surface with light from a light source, the illumination optical system comprising a polarization converting unit according to claim 18, which is arranged in an optical path between the light source and the illumination target surface.

32. An illumination optical system according to claim 31, wherein the polarization converting unit is arranged in a pupil space including an illumination pupil of the illumination optical system.

33. An illumination optical system according to claim 32, the illumination optical system being used in combination with a projection optical system for forming a plane optically conjugate with the illumination target surface, wherein the illumination pupil is arranged at a position optically conjugate with an aperture stop of the projection optical system.

34. An exposure apparatus configured to expose a photosensitive substrate to transfer a predetermined pattern thereto, the exposure apparatus comprising an illumination optical system according to claim 31 configured to illuminate the predetermined pattern.

35. An exposure apparatus according to claim 34, further comprising a projection optical system configured to form an image of the predetermined pattern on the photosensitive substrate.

36. A device manufacturing method, comprising:

exposing a photosensitive substrate to transfer a predetermined pattern thereto, using an exposure apparatus according to claim 34;

developing the photosensitive substrate to which the predetermined pattern is transferred, thereby to form a mask layer in a shape corresponding to the predetermined pattern on a surface of the photosensitive substrate; and

processing the surface of the photosensitive substrate through the mask layer.