Illumination apparatus, illumination method, exposure apparatus, and device manufacturing method

• US 9,116,346 B2
• Filed: 10/22/2008
• Issued: 08/25/2015
• Est. Priority Date: 11/06/2007
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Tanitsu, Osamu
• Primary Examiner(s): Kim, Peter B
• Application Number:
  US12/256,055
• Publication Number:
  US 20090116093A1
• Time in Patent Office: 2,498 Days
• Field of Search: 355/67, 355/71, 359/237
• US Class Current: 1/1
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• 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 27/0905 Dividing and/or superposing multiple light beams
• CPC Class Codes: G03F 7/70058 Mask illumination systems
• CPC Class Codes: G03F 7/70075 Homogenization of illumination intensity in the mask plane by using an integrator, e.g. fly's eye lens, facet mirror or glass rod, by using a diffusing optical element or by beam deflection
• CPC Class Codes: G03F 7/70108 Off-axis setting using a light-guiding element, e.g. diffractive optical elements [DOEs] or light guides
• 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

Abstract

To optionally forming a multilevel light intensity distribution on an illumination pupil plane, the illumination apparatus implements Köhler illumination on an illumination target surface, using as a light source the light intensity distribution formed on the illumination pupil plane on the basis of light from a light source. The illumination apparatus has a spatial light modulator, a condensing optical system, and a control unit. The spatial light modulator has a plurality of reflecting surfaces which are two-dimensionally arranged and postures of which can be controlled independently of each other. The condensing optical system condenses light from the reflecting surfaces to form a predetermined light intensity distribution on the illumination pupil plane. The control unit controls the number of reflecting surfaces contributing to arriving light, for each of points on the illumination pupil plane forming the light intensity distribution, according to a light intensity distribution to be formed on the illumination pupil plane.

Claims

1. An illumination apparatus which forms a predetermined pupil intensity distribution on an illumination pupil plane by light from a light source and illuminates an illumination target surface with light from the predetermined pupil intensity distribution, the illumination apparatus comprising:

a spatial light modulator having a plurality of reflecting surfaces arranged two-dimensionally, postures of the respective reflecting surfaces being controlled independently of each other;

a condensing optical system, arranged between the light source and a position where the predetermined pupil intensity distribution is formed, configured to convert light provided with a predetermined angle distribution by the plurality of reflecting surfaces of the spatial light modulator into a position distribution on a predetermined surface, to form a predetermined light intensity distribution on the predetermined surface;

a fly'"'"'s eye optical system having a plurality of optical surfaces arranged two-dimensionally on the predetermined surface, configured to form the predetermined pupil intensity distribution on the illumination pupil plane by light from the condensing optical system; and

a controller configured to feed a control signal to the spatial light modulator according to the predetermined pupil intensity distribution formed on the illumination pupil plane;

wherein

the predetermined light intensity distribution includes at least a first zone with a first light intensity, a second zone with a second light intensity different from the first light intensity, and a third zone with a third light intensity different from the first and second light intensities, and

the controller is configured to control the postures of the plurality of reflecting surfaces so that, among the plurality of reflecting surfaces, a number of reflecting surfaces of a first group, a number of reflecting surfaces of a second group, and a number of reflecting surfaces of a third group are different from each other, so that light from the reflecting surfaces of the first group reaches the first zone via the condensing optical system, so that light from the reflecting surfaces of the second group reaches the second zone via the condensing optical system, and so that light from the reflecting surfaces of the third group reaches the third zone via the condensing optical system.

2. The illumination apparatus according to claim 1, wherein,

in the case that there is a remainder when a number of the reflecting surfaces in the spatial light modulator is divided by a total number of reflecting surfaces necessary for formation of the pupil intensity distribution on the illumination pupil plane, the controller controls the postures of the respective reflecting surfaces so that light reflected by remaining reflecting surfaces is guided to a region other than the illumination pupil plane.

3. The illumination apparatus according to claim 2, further comprising

an intensity distribution measuring device for performing measurement of the pupil intensity distribution formed on the illumination pupil plane,

wherein the controller controls the postures of the reflecting surfaces in the spatial light modulator, based on a result of the measurement from the intensity distribution measuring device.

4. The illumination apparatus according to claim 1, further comprising

an intensity distribution measuring device for performing measurement of the pupil intensity distribution formed on the illumination pupil plane,

wherein the controller controls the postures of the plurality of reflecting surfaces in the spatial light modulator, based on a result of the measurement from the light-intensity distribution measuring device.

5. The illumination apparatus according to claim 1, wherein

the spatial light modulator comprises a drive unit for individually changing the postures of the plurality of reflecting surfaces on the basis of a control signal from the controller.

6. The illumination apparatus according to claim 5, wherein

the drive unit continuously or discretely changes orientations of the plurality of reflecting surfaces.

7. The illumination apparatus according to claim 6, wherein

the reflecting surfaces contributing to light arriving at a predetermined point on the illumination pupil plane are subjected to such posture control that normals to the respective reflecting surfaces become parallel to each other.

8. An exposure apparatus comprising an illumination apparatus as set forth in claim 1 which illuminates a predetermined pattern, the exposure apparatus exposing the predetermined pattern on a photosensitive substrate.

9. A device manufacturing method comprising:

effecting the exposure of the predetermined pattern on the photosensitive substrate, using the exposure apparatus of claim 8;

developing the photosensitive substrate onto which the predetermined pattern has been transferred, and then forming 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.

10. The illumination apparatus according to claim 1, further comprising:

an optical integrator arranged at a rear side of the condensing optical system in a traveling direction of the illumination light.

11. An illumination method of forming a predetermined pupil intensity distribution on an illumination pupil plane by light from a light source and illuminating an illumination target surface with light from the predetermined pupil intensity distribution, the illumination method comprising:

reflecting light from the light source by a plurality of reflecting surfaces, postures of which are controlled independently of each other and which are two-dimensionally arranged;

converting light, a predetermined angle distribution of which is provided by the plurality of reflecting surfaces reflecting the light, into a position distribution on a predetermined surface, while guiding the light to a plurality of optical surfaces arranged two-dimensionally on the predetermined surface;

forming a predetermined light intensity distribution on the predetermined surface, the predetermined light intensity distribution including at least a first zone with a first light intensity, a second zone with a second light intensity different from the first light intensity, and a third zone with a third light intensity different from the first and second light intensities, the first to third zones being zones on the illumination pupil plane;

forming the predetermined pupil intensity distribution on the illumination pupil plane by light via the plurality of optical surfaces; and

controlling the postures of the plurality of the reflecting surfaces so that, among the plurality of reflecting surfaces, a number of reflecting surfaces of a first group, a number of reflecting surfaces of a second group, and a number of reflecting surfaces of a third group are different from each other, so that light from the reflecting surfaces of the first group reaches the first zone, so that light from the reflecting surfaces of the second group reaches the second zone, and so that light from the reflecting surfaces of the third group reaches the third zone.

12. The illumination method according to claim 11, wherein,

in the case that there is a remainder when a number of the reflecting surfaces is divided by a total number of reflecting surfaces necessary for formation of the pupil intensity distribution on the illumination pupil plane, the postures of the respective reflecting surfaces are controlled so that light reflected by remaining reflecting surfaces is guided to a region other than the illumination pupil plane.

13. The illumination method according to claim 11, wherein

the postures of the reflecting surfaces are controlled based on a result of measurement of the pupil intensity distribution formed on the illumination pupil plane.

14. The illumination method according to claim 11, wherein

orientations of the reflecting surfaces are continuously or discretely changed.

15. The illumination method according to claim 11, wherein

the reflecting surfaces contributing to light arriving at a predetermined point on the illumination pupil plane are subjected to such posture control that normals to the respective reflecting surfaces are parallel to each other.

16. The illumination method according to claim 11, further comprising:

passing the light through an optical integrator after the light has passed through the condensing optical system.

17. An illumination apparatus which illuminates an illumination target surface with light from a light source, the illumination apparatus comprising:

a spatial light modulator having a plurality of reflecting surfaces arranged two-dimensionally, postures of the respective reflecting surfaces being controlled independently of each other;

a first condensing optical system, arranged between the spatial light modulator and the illumination target surface, configured to condense light from the plurality of reflecting surfaces of the spatial light modulator onto a predetermined surface in an optical path of the illumination apparatus;

a fly'"'"'s eye optical system having a plurality of optical surfaces arranged two-dimensionally on the predetermined surface, configured to form a light intensity distribution on an illumination pupil plane by light from the first condensing optical system; and

a controller configured to control the plurality of reflecting surfaces of the spatial light modulator, wherein

the controller controls reflecting surfaces, belonging to a first group, among the plurality of reflecting surfaces so that light from the reflecting surfaces of the first group reaches a first zone on the predetermined surface, controls reflecting surfaces, belonging to a second group different from the first group, among the plurality of reflecting surfaces so that light from the reflecting surfaces of the second group reaches a second zone different from the first zone on the predetermined surface, and controls reflecting surfaces, belonging to a third group different from the first and second groups, among the plurality of reflecting surfaces so that light from the reflecting surfaces of the third group reaches a third zone different from the first and second zones on the predetermined surface,

a number of the reflecting surfaces of the first group, a number of the reflecting surfaces of the second group, and a number of the reflecting surfaces of the third group are different from each other, and

a light intensity of the first zone, a light intensity of the second zone, and a light intensity of the third zone are different from each other.

18. The illumination apparatus according to claim 17, further comprising:

a second condensing optical system arranged between the illumination pupil plane and the illumination target surface, the second condensing optical system being configured to condense light from the illumination pupil plane onto the illumination target surface.

19. The illumination apparatus according to claim 18, wherein

the second condensing optical system causes a condition that the illumination target surface becomes an optical Fourier transform surface of the illumination pupil plane.

20. The illumination apparatus according to claim 18, wherein

the illumination apparatus is used together with a projection optical system which projects a pattern arranged on the illumination target surface onto an image surface.

21. The illumination apparatus according to claim 17, wherein

the spatial light modulator is arranged near a front focal point of the first condensing optical system.

22. The illumination apparatus according to claim 21, wherein

a rear focal point of the first condensing optical system is located on the predetermined surface.

23. The illumination apparatus according to claim 17, wherein

a region in which the reflecting surfaces of the first group are located, a region in which the reflecting surfaces of the second group are located, and a region in which the reflecting surfaces of the third group are located do not overlap each other on the spatial light modulator.

24. The illumination apparatus according to claim 17, wherein

in the case that there is a remainder when a number of the plurality of reflecting surfaces of the spatial light modulator is divided by a total number of reflecting surfaces necessary for formation of the light intensity distribution on the illumination pupil plane, the controller respectively controls postures of the plurality of reflecting surfaces so that light reflected by remaining reflecting surfaces is guided to a region other than the illumination pupil plane.

25. An illumination method which illuminates an illumination target surface with light from a light source, the illumination method comprising:

reflecting the light from the light source by a plurality of reflecting surfaces arranged two-dimensionally, respective postures of the plurality of reflecting surfaces being controlled independently of each other;

guiding light reflected by the plurality of reflecting surfaces onto a plurality of optical surfaces arranged two-dimensionally on a predetermined surface; and

forming a light intensity distribution on an illumination pupil plane by light going through the plurality of optical surfaces, wherein

the reflecting includes;

controlling postures of reflecting surfaces, belonging to a first group, among the plurality of reflecting surfaces so that light from the reflecting surfaces of the first group reaches a first zone on the predetermined surface, controlling postures of reflecting surfaces, belonging to a second group different from the first group, among the plurality of reflecting surfaces so that light from the reflecting surfaces of the second group reaches a second zone different from the first zone on the predetermined surface; and

controlling postures of reflecting surfaces, belonging to a third group different from the first and second groups, among the plurality of reflecting surfaces so that light from the reflecting surfaces of the third group reaches a third zone different from the first and second zones on the predetermined surface,

a number of the reflecting surfaces of the first group, a number of the reflecting surfaces of the second group, and a number of the reflecting surfaces of the third group are different from each other, and

a light intensity of the first zone, a light intensity of the second zone, and a light intensity of the third zone are different from each other.

26. The illumination method according to claim 25, further comprising:

condensing light from the illumination pupil plane onto the illumination target surface.

27. The illumination method according to claim 26, wherein

the condensing includes causing a condition that the illumination target surface becomes an optical Fourier transform surface of the illumination pupil plane.

28. The illumination method according to claim 26, wherein

the illumination method is used for projecting a pattern arranged on the illumination target surface onto an image surface by using a projection optical system, and

a surface having an aperture stop of the projection optical system and the illumination pupil plane are conjugate with each other.

29. The illumination method according to claim 25, wherein

the guiding is performed by a condensing optical system, and

a surface on which the plurality of reflecting surfaces are two-dimensionally arranged is located near a front focal point of the condensing optical system.

30. The illumination method according to claim 29, wherein

a rear focal point of the condensing optical system is located on the predetermined surface.

31. The illumination method according to claim 25, wherein

a region in which the reflecting surfaces of the first group are located, a region in which the reflecting surfaces of the second group are located, and a region in which the reflecting surfaces of the third group are located do not overlap each other on a surface on which the plurality of reflecting surfaces are two-dimensionally arranged.

32. The illumination method according to claim 25, wherein

in the case that there is a remainder when a number of the plurality of reflecting surfaces is divided by a total number of reflecting surfaces necessary for formation of the pupil intensity distribution on the illumination pupil plane, the reflecting includes respectively controlling postures of the plurality of reflecting surfaces so that light reflected by remaining reflecting surfaces is guided to a region other than the illumination pupil plane.