Illumination optical assembly, exposure apparatus, and device manufacturing method

• US 9,513,560 B2
• Filed: 04/24/2014
• Issued: 12/06/2016
• Est. Priority Date: 10/24/2011
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Tanaka, Hirohisa, Ooki, Hiroshi, Nakajima, Shinichi
• Primary Examiner(s): Kim, Peter B
• Application Number:
  US14/261,194
• Publication Number:
  US 20140307245A1
• Time in Patent Office: 957 Days
• Field of Search: 355/71
• US Class Current: 1/1
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 5/3075 for use in the UV G02B5/3066 takes precedence
• 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

Abstract

An illumination optical system can form a pupil intensity distribution with a desired beam profile. The illumination optical system for illuminating an illumination target surface with light from a light source is provided with a spatial light modulator which has a plurality of optical elements arrayed on a predetermined surface and individually controlled and which variably forms a light intensity distribution on an illumination pupil of the illumination optical system; a divergence angle providing member which is arranged in a conjugate space including a surface optically conjugate with the predetermined surface and which provides a divergence angle to an incident beam and emits the beam; and a polarizing member which is arranged at a position in the vicinity of the predetermined surface or in the conjugate space and which changes a polarization state of a partial beam of a propagating beam propagating in an optical path.

Claims

1. An illumination optical system which illuminates an illumination target surface with light, the illumination optical system comprising:

a spatial light modulator having a plurality of optical elements arrayed on a predetermined surface and individually controlled, the spatial light modulator being configured to variably form a light intensity distribution on an illumination pupil of the illumination optical system;

a divergence angle providing member arranged in a conjugate space in which a surface optically conjugate with the predetermined surface is disposed, the divergence angle providing member being configured to provide a divergence angle to an incident beam and emit the beam; and

a polarizing member arranged in a predetermined space in which the predetermined surface is disposed or in the conjugate space, the polarizing member being configured to change a polarization state of a partial beam which is a part of the light.

2. The illumination optical system according to claim 1, wherein the polarizing member is arranged on a first surface which is a surface in an illumination optical path of the illumination optical system and wherein the light passing the first surface is incident to the spatial light modulator.

3. The illumination optical system according to claim 1, wherein the polarizing member is arranged on a first surface which is a surface in an illumination optical path of the illumination optical system and wherein the light passing the first surface is incident to the divergence angle providing member.

4. The illumination optical system according to claim 1, wherein the polarizing member is arranged on a surface optically conjugate with the predetermined surface.

5. The illumination optical system according to claim 1, wherein the divergence angle providing member is arranged only in a first optical path in which at least a partial beam travels, and has such a characteristic that when a parallel beam is incident thereto, the divergence angle providing member converts the incident beam into a divergent beam with a predetermined divergence angle and emits the divergent beam.

6. The illumination optical system according to claim 5, comprising an input device for implementing input of light quantity distribution information of a target image on a first surface,

wherein the spatial light modulator has N optical elements, the optical elements being configured to guide the light to respective local regions at positions variable on the first surface and capable of being divided into K optical element groups, where N is an integer larger than K and K is an integer of not less than 2, and

the illumination optical system further comprises:

K filter portions configured to control variables about states of the local regions in K groups guided to the first surface by the K optical element groups, group by group;

an arithmetic unit configured to determine N first values of the positions and N1 values of the variables of the local regions, depending upon an error between a first image obtained by arranging N aforementioned local regions on the first surface and the target image, divide the N local regions into the K groups depending upon the N1 values of the variables, and determine common second values as values of the variables for the respective K groups, where N1 is an integer not more than N and larger than K; and

a condenser optical system configured to illuminate the illumination target surface with light from a light quantity distribution of a second image formed on the first surface while setting the positions of the corresponding local regions for the respective K optical elements, to the first values, and setting the variables to the second values.

7. The illumination optical system according to claim 6, wherein, for dividing the N local regions into the K groups depending upon the N1 values of the variables, the arithmetic unit is configured to implement clustering to partition the N local regions into K groups each with values of the variables having smaller discrepancies.

8. The illumination optical system according to claim 6, wherein the K filter portions are:

K filter member groups which are arranged at positions corresponding to the K optical element groups on a second surface conjugate with an average arrangement surface of the optical elements or on a plane in the vicinity thereof and in which divergence angles of light can be controlled in a plurality of stages independently of each other.

9. The illumination optical system according to claim 6, comprising a measuring device which measures a light quantity distribution of an image formed on the first surface,

wherein the arithmetic unit is configured to correct the first values of the positions and the second values of the variables, based on the measurement result by the measuring device.

10. The illumination optical system according to claim 6, wherein the N1 values of the variables are N values.

11. The illumination optical system according to claim 6, wherein the optical elements are reflective elements whose inclination angles about two intersecting axes can be controlled.

12. The illumination optical system according to claim 1, wherein the divergence angle providing member comprises:

a first region having such a characteristic that when a parallel beam is incident thereto, the first region converts the incident beam into a first divergent beam with a first divergence angle and emits the first divergent beam; and

a second region having such a characteristic that when a parallel beam is incident thereto, the second region converts the incident beam into a second divergent beam with a second divergence angle and emits the second divergent beam.

13. The illumination optical system according to claim 12, comprising a light intensity distribution setting unit arranged in an optical path on the entrance side of the divergence angle providing member, the light intensity distribution setting unit being configured to set a light intensity distribution in which an intensity of light incident to the second region is higher than an intensity of light incident to the first region.

14. The illumination optical system according to claim 1, wherein a plurality of beams with mutually different divergence angles are emitted from the divergence angle providing member and wherein the plurality of beams with the different divergence angles pass at mutually different positions on a plane crossing the optical axis of the illumination optical system.

15. The illumination optical system according to claim 1, wherein the divergence angle providing member is interchangeable with another divergence angle providing member with a different characteristic.

16. The illumination optical system according to claim 15, wherein a first divergence angle distribution which is defined as a distribution on a plane crossing the optical axis of the illumination optical system, of divergence angles of beams emitted from the divergence angle providing member with incidence of a parallel beam to the divergence angle providing member and a second divergence angle distribution which is defined as a distribution on the plane crossing the optical axis of the illumination optical system, of divergence angles of beams emitted from the other divergence angle providing member with incidence of a parallel beam to the other divergence angle providing member are distributions different from each other.

17. The illumination optical system according to claim 1, wherein the polarizing member has:

a first polarizing element configured to change a first beam incident thereto into light in a first polarization state; and

a second polarizing element configured to change a second beam incident thereto into light in a second polarization state, and

wherein the second beam is parallel to the first beam.

18. The illumination optical system according to claim 1, wherein the polarizing member is configured to provide a phase difference between a first polarization component of an incident beam and a second polarization component thereof in a polarization state different from that of the first polarization component.

19. The illumination optical system according to claim 1, wherein the polarizing member has a wave plate arranged only in a first optical path in which the partial beam travels.

20. The illumination optical system according to claim 1, wherein the polarizing member has an azimuth rotator arranged only in a first optical path in which the partial beam travels.

21. The illumination optical system according to claim 1, comprising an optical integrator,

wherein the polarizing member is arranged in an optical path on an incidence side of the optical integrator.

22. The illumination optical system according to claim 1, comprising a light intensity homogenizing member arranged on a second predetermined surface in an optical path on the entrance side of the spatial light modulator, the light intensity homogenizing member being configured to make homogeneity in the predetermined surface of an intensity distribution of light incident to the predetermined surface higher than homogeneity in the second predetermined surface of an intensity distribution of light incident to the second predetermined surface.

23. The illumination optical system according to claim 22, wherein the light intensity homogenizing member has:

a wavefront division element for implementing wavefront division of an incident beam into a plurality of beams; and

a relay optical system which superimposes the plurality of beams resulting from the wavefront division by the wavefront division element, on the predetermined surface.

24. The illumination optical system according to claim 23, wherein the wavefront division element is arranged at a front focal position of the relay optical system and wherein a rear focal position of the relay optical system is located at the predetermined surface.

25. The illumination optical system according to claim 23, comprising a beam detection unit which detects at least one of a position in a plane crossing the optical path of the light incident to the predetermined surface, and an angle to the predetermined surface, of the light incident to the predetermined surface, based on light extracted from an optical path between the wavefront division element and the spatial light modulator.

26. The illumination optical system according to claim 1, comprising a polarization conversion unit arranged in the vicinity of the illumination pupil, the polarization conversion unit being configured to convert linearly-polarized incident light with a polarization direction along a predetermined direction, into circumferentially-polarized emergent light with a polarization direction along a tangent direction to a circle centered on the optical axis of the illumination optical system or into radially-polarized emergent light with a polarization direction along a radial direction of the circle.

27. The illumination optical system according to claim 26, wherein the polarization conversion unit has a polarization conversion member which is made of an optical material with optical rotatory power and which has a form in which thickness varies along a circumferential direction of the circle centered on the optical axis.

28. The illumination optical system according to claim 27, wherein the polarization conversion member has a shape in which thickness continuously varies along the circumferential direction of the circle centered on the optical axis.

29. The illumination optical system according to claim 1, wherein the spatial light modulator has a plurality of mirror elements two-dimensionally arrayed in the predetermined surface, and a drive unit for individually controlling and driving postures of the plurality of mirror elements.

30. The illumination optical system according to claim 1, comprising a distribution forming optical system arranged in an optical path between the spatial light modulator and the illumination pupil, the distribution forming optical system being configured to image a far field pattern formed in a far field by the plurality of optical elements of the spatial light modulator, on the illumination pupil.

31. The illumination optical system according to claim 30, wherein the distribution forming optical system is configured to convert a distribution of angular directions of emergent beams from the spatial light modulator into a position distribution on a cross section of an emergent beam from the distribution forming optical system.

32. The illumination optical system according to claim 30, wherein a front focal position of the distribution forming optical system is located in the predetermined space and wherein a rear focal position of the distribution forming optical system is located in a pupil space of the illumination optical system.

33. The illumination optical system according to claim 1, which is used in combination with a projection optical system which forms a surface optically conjugate with the illumination target surface, wherein the illumination pupil is a position optically conjugate with an aperture stop of the projection optical system.

34. An exposure apparatus comprising the illumination optical system according to claim 1 which illuminates a predetermined pattern, the exposure apparatus being configured to expose a photosensitive substrate with the predetermined pattern.

35. The exposure apparatus according to claim 34, comprising a projection optical system which forms an image of the predetermined pattern on the photosensitive substrate, wherein the illumination pupil is a position optically conjugate with an aperture stop of the projection optical system.

36. A device manufacturing method comprising:

performing the exposure of the photosensitive substrate with the predetermined pattern, using the exposure apparatus according to claim 34;

developing the photosensitive substrate on which the predetermined pattern has been transferred, 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.

37. An illumination optical system which illuminates an illumination target surface with light, the illumination optical system comprising:

a spatial light modulator having a plurality of optical elements arrayed on a predetermined surface and individually controlled, the spatial light modulator being configured to form a light intensity distribution on an illumination pupil of the illumination optical system; and

a divergence angle providing member arranged in a conjugate space in which a surface optically conjugate with the predetermined surface is disposed, the divergence angle providing member being configured to provide a divergence angle to at least a partial beam which is a part of the light, to generate a plurality of beams with different divergence angles.

38. The illumination optical system according to claim 37, wherein the plurality of beams with the mutually different divergence angles are emitted from the divergence angle providing member and wherein the plurality of beams with the different divergence angles pass at mutually different positions on a plane crossing the optical axis of the illumination optical system.

39. The illumination optical system according to claim 37, wherein the divergence angle providing member is arranged in a first optical path in which the partial beam travels, and has such a characteristic that when a parallel beam is incident thereto, the divergence angle providing member converts the incident beam into a divergent beam with a predetermined divergence angle and emits the divergent beam.

40. The illumination optical system according to claim 37, wherein the divergence angle providing member comprises:

a first region having such a characteristic that when a parallel beam is incident thereto, the first region converts the incident beam into a first divergent beam with a first divergence angle and emits the first divergent beam; and

a second region having such a characteristic that when a parallel beam is incident thereto, the second region converts the incident beam into a second divergent beam with a second divergence angle and emits the second divergent beam.

41. The illumination optical system according to claim 40, comprising a light intensity distribution setting unit arranged in an optical path on the entrance side of the divergence angle providing member, the light intensity distribution setting unit is configured to set a light intensity distribution in which an intensity of light incident to the second region is higher than an intensity of light incident to the first region.

42. The illumination optical system according to claim 37, wherein the divergence angle providing member is interchangeable with another divergence angle providing member with a different characteristic.

43. The illumination optical system according to claim 42, wherein a first divergence angle distribution which is defined as a distribution on a plane crossing the optical axis of the illumination optical system, of divergence angles of beams emitted from the divergence angle providing member with incidence of a parallel beam to the divergence angle providing member and a second divergence angle distribution which is defined as a distribution on the plane crossing the optical axis of the illumination optical system, of divergence angles of beams emitted from the other divergence angle providing member with incidence of a parallel beam to the other divergence angle providing member are distributions different from each other.

44. The illumination optical system according to claim 37, comprising a polarizing member arranged in a predetermined space in which the predetermined surface is disposed or in the conjugate space, the polarizing member being configured to change a polarization state of the partial beam.

45. The illumination optical system according to claim 44, wherein the polarizing member has:

a first polarizing element configured to change a first beam incident thereto into light in a first polarization state; and

a second polarizing element configured to change a second beam incident thereto into light in a second polarization state, and

wherein the second beam is parallel to the first beam.

46. The illumination optical system according to claim 44, wherein the polarizing member has a wave plate arranged only in a first optical path in which the partial beam travels.

47. The illumination optical system according to claim 44, wherein the polarizing member has an azimuth rotator arranged only in a first optical path in which the partial beam travels.

48. The illumination optical system according to claim 44, comprising an optical integrator,

wherein the polarizing member is arranged in an optical path on an incidence side of the optical integrator.