Illumination optical system, exposure apparatus, and exposure method

• US 20080094602A1
• Filed: 11/05/2007
• Published: 04/24/2008
• Est. Priority Date: 12/03/2002
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Tanaka, Hirohisa, Tanitsu, Osamu, Muramatsu, Kenichi, Matsuyama, Tomoyuki, Komine, Norio, Kudo, Takehito, Nishinaga, Hisashi
• Granted Patent: US 7,515,247 B2
• Time in Patent Office: Days
• US Class Current: 355/71
• CPC Class Codes: G03B 27/42 for automatic sequential copying of the same original G03B27/34, G03B27/53 take 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 7/70566 Polarisation control

Abstract

An illumination optical system for, when installed in an exposure system, realizing a suitable illumination condition by varying the polarized state of the illumination light according to the pattern characteristics of the mask while suppressing the loss of the intensity of the light. The illumination optical system has a light source unit for supplying a linearly polarized light for illuminating surfaces to be illuminated therewith, and a polarized state changing device for changing the polarized state of the illuminating light from a predetermined polarized state to a nonpolarized state and vice versa. The polarized state changing device is arranged in the optical path between the light source unit and the surfaces to be illuminated. The polarized state changing device can be removed from the illumination optical path and has a depolarizer for selectively depolarizing the incident linearly polarized light.

Claims

1. An illumination optical system that illuminates an illuminated surface with light including a predetermined polarized state supplied from a light source, comprising:

a light directing device that directs the light from the light source to the illuminated surface, the light directing device being positioned in a light path between the light source and the illuminated surface; and

a polarized state fluctuation correcting device that corrects fluctuations in the polarized state on the illuminated surface, the polarized state fluctuation correcting device being positioned in the light path between the light source and the illuminated surface.

2. The illumination optical system of claim 1, wherein the polarized state fluctuation correcting device comprises:

a polarized state adjusting device that adjust the polarized state on the illuminated surface, the polarized state adjusting device being positioned in the light path between the light source and the illuminated surface;

a polarization monitor that detects the polarized state of the light, the polarization monitor being positioned in the light path between the light source and the illuminated surface; and

a controller that controls the polarized state adjusting device in accordance with an output from the polarization monitor.

3. The illumination optical system of claim 2, wherein the polarized state adjusting device comprises an adjustable phase plate positioned in the light path between the light source and the polarization monitor.

4. The illumination optical system of claim 1, wherein the light directing device comprises an optical member including a characteristic that changes the polarized state of incident light that it ejects.

5. The illumination optical system of claim 4, wherein the optical member is formed by a crystal optical material.

6. The illumination optical system of claim 1, wherein the polarized state fluctuation correcting device corrects fluctuations in the polarized state on the illuminated surface, which originates in a light transmissive member in the light directing device.

7. The illumination optical system of claim 6, wherein the light transmissive member is formed by a crystal optical material.

8. The illumination optical system of claim 7, wherein the light transmissive member is formed by a cubic system crystal material and positioned in the light path between the light source and the illuminated surface, the light transmissive member being configured such that a traveling direction of the light becomes closer to a crystal orientation <

111>

or <

100>

than to a crystal orientation <

110>

.

9. The illumination optical system of claim 8, wherein

the polarized state fluctuation correcting device comprises a polarized state adjusting device that is positioned in the light path between the light source and the illuminated surface and that adjusts the polarized state on the illuminated surface, and

the light transmissive member is formed by a cubic system crystal material and is positioned in the light path between the light source and the polarized state adjusting device, the light transmissive member being configured such that a traveling direction of the light becomes closer to a crystal orientation <

111>

or <

100>

than to a crystal orientation <

110>

.

10. The illumination optical system of claim 8, wherein the light transmissive member includes an optical member fixedly positioned in the light path, and an optical axis of the optical member is configured to substantially match the crystal orientation <

111>

or <

100>

.

11. The illumination optical system of claim 8, wherein the light transmissive member includes a rectangular prism as a rear surface reflection mirror,

an incident surface and an exit surface of the rectangular prism are configured to substantially match a crystal plane {100}, and

a reflection surface of the rectangular prism is configured to substantially match a crystal plane {110}.

12. The illumination device of claim 8, wherein the light transmissive member includes a plane parallel plate for moving light entering along the optical axis in parallel, the light transmissive member being provided in the light path and inclinable with respect to the optical axis, and

the optical axis of the plane parallel plate is configured to substantially match the crystal orientation <

100>

.

13. The illumination optical system of claim 1, wherein the polarized state fluctuation correction device corrects time-lapse fluctuations of the polarized state on the illuminated surface.

14. The illumination optical system of claim 1, wherein the polarized state fluctuation correct device kinematically holds an optical element disposed in the light path between the light source and the illuminated surface.

15. An exposure apparatus, comprising the illumination optical system of claim 1.

16. The exposure apparatus of claim 15, further comprising:

a projection optical system positioned in the light path between a first plane at which the mask is positioned, and a second plane at which the photosensitive substrate is positioned, the projection optical system forming an image of a pattern on the mask onto the second plane;

a pupil intensity distribution forming device that forms a predetermined light intensity distribution at a position conjugate to a pupil of the projection optical system or a position adjacent thereto; and

a pupil intensity distribution changing device that changes at least one of a shape and a size of the predetermined light intensity distribution.

17. The exposure apparatus of claim 16, further comprising a polarized state changing device that is positioned in the light path between the light source and the illuminated surface and changes the polarized state of the light that illuminates the illuminated surface, wherein

the pupil intensity distribution changing device changes at least one of the shape and the size of the predetermined light intensity distribution in accordance with pattern characteristics of the mask, and

the polarized state changing device changes the polarized state of the light that illuminates the illuminated surface in accordance with at least one of the shape and the size of the predetermined light intensity distribution.

18. The exposure apparatus of claim 17, wherein

the polarized state changing device comprises a polarized state switching device that switches the polarized state of the light that illuminates the illuminated surface between a predetermined polarized state and a nonpolarized state, and

the polarized state switching device switches between the predetermined polarized state and the nonpolarized state in accordance with a change in at least one of the shape and the size of the predetermined light intensity distribution.

19. The exposure apparatus of claim 17, wherein

the pupil intensity distribution forming device forms two areas including a high light intensity distribution that are spaced away from each other along a pitch direction of a line-and-space pattern formed on the mask, and

the polarized state changing device sets the polarized state of the light that illuminates the illuminated surface from the two areas including a high light intensity distribution to a linearly polarized state that includes a polarization plane in a direction orthogonal to the pitch direction.

20. The exposure apparatus of claim 19, wherein the two areas including a high light intensity distribution are formed symmetrically about the optical axis of the illumination optical system, and

a value σ

o defined by a ratio φ

o/φ

p satisfies the following condition;

0.7≦

σ

o

where φ

o is a diameter of a circle about the optical axis that circumscribes the two areas including a high light intensity distribution, and φ

p is a diameter of the pupil plane.

21. The exposure apparatus of claim 19, wherein the two areas including a high light intensity distribution are formed symmetrically about the optical axis of the illumination optical system, and

a value σ

o defined by a ratio φ

o/φ

p and σ

i defined by a ratio φ

i/φ

p satisfy the following condition;

0.5≦

σ

o/σ

i

where φ

o is a diameter of a circle about the optical axis that circumscribes the two areas including a high light intensity distribution, φ

p is a diameter of the pupil plane, and φ

i is a diameter of a circle about the optical axis that inscribes the two areas including a high light intensity distribution.

22. The exposure apparatus of claim 17, wherein

the pupil intensity distribution forming device forms one area including a high light intensity distribution substantially about the optical axis of the illumination optical system, and

the polarized state changing device sets the polarized state of the light that illuminates the illuminated surface from the one area including a high light intensity distribution to the linearly polarized state that includes a polarization plane in a direction substantially orthogonal to the pitch direction of the line-and-space pattern formed on a phase shift mask as the mask.

23. The exposure apparatus of claim 22, wherein a value σ

that is defined by a ratio φ

o/φ

p satisfies the following condition;

σ

≦

0.4

where  

is a size of the one area including a high light intensity distribution, and φ

p is a diameter of the pupil plane.

24. An exposure method, comprising:

illuminating a mask through the illumination optical system of claim 1;

and

exposing an image of a pattern on the mask onto the photosensitive substrate positioned on the illuminated surface.

25. The exposure method of claim 24, further comprising:

forming the image of the pattern on the mask using a projection optical system;

forming a predetermined light intensity distribution at a position conjugate to a pupil of the projection optical system or a position adjacent thereto; and

changing at least one of a shape or a size of the predetermined light intensity distribution.

26. The exposure method of claim 25, wherein the changing the at least one of a shape or a size of the predetermined light intensity distribution changes at least one of the shape and the size of the predetermined light intensity distribution in accordance with pattern characteristics of the mask;

the exposure method further comprises changing a polarized state of the light that illuminates the illuminated surface in accordance with a change in the at least one of the shape and the size of the predetermined light intensity distribution.

27. The exposure method of claim 26, wherein the forming the predetermined light intensity distribution forms two areas including a high light intensity distribution spaced away from each other along a pitch direction of a line-and-space pattern formed on the mask, the exposure method further comprising setting the polarized state of the light that illuminates the illuminated surface from the two areas including a high light intensity distribution to a linearly polarized state that includes a polarization plane in a direction substantially orthogonal to the pitch direction.

28. The exposure method of claim 27, wherein

the two areas including a high light intensity distribution are formed symmetrically about the optical axis of the illumination optical system, and

a value σ

o defined by a ratio φ

o/φ

p satisfies the following condition;

0.7≦

σ

o

where φ

o is a diameter of a circle about the optical axis that circumscribes the two areas including a high light intensity distribution, and φ

p is a diameter of the pupil plane.

29. The exposure method of claim 27, wherein

the two areas including a high light intensity distribution are formed symmetrically about the optical axis of the illumination optical system, and

a value σ

o defined by a ratio φ

o/φ

p and σ

i defined by a ratio φ

i/φ

p satisfy the following condition;

0.5≦

σ

i/σ

o

where σ

o is a diameter of a circle about the optical axis that circumscribes the two areas including a high light intensity distribution, φ

p is a diameter of the pupil plane, and φ

i is a diameter of a circle about the optical axis that inscribes the two areas including a high light intensity distribution.

30. An exposure method for exposing a pattern on a mask positioned at a first plane onto a photosensitive substrate positioned at a second plane, comprising:

providing light;

illuminating the mask with the light provided in the first step;

exposing the pattern on the mask illuminated in the second step onto the photosensitive substrate; and

correcting fluctuations of a polarized state of the light on the second plane.

31. The exposure method of claim 30, further comprising detecting the polarized state of the light, wherein the correcting fluctuations of a polarized state of the light on the second plane includes adjusting the polarized state on the second plane based on the polarized state of the detected light.

32. The exposure method of claim 30, wherein the correcting fluctuations of a polarized state of the light on the second plane corrects the fluctuation of the polarized state of the light on the second plane that originates in a light transmissive member in a light path of the provided light.

33. The exposure method of claim 30, wherein a time-lapse fluctuation of the polarized state on the second surface is corrected in the correcting fluctuations of a polarized state of the light on the second plane.