Illumination device for projection exposure apparatus

Claims

What is claimed is:

1. An illumination device, comprising:

secondary light source forming means having a deflecting member with a conical light deflecting surface for transforming received light into substantially ring-like light, said secondary light source forming means forming a ring-like secondary light source by using the ring-like light; and

an optical system for projecting divergent lights from portions of the secondary light source obliquely onto a surface to be illuminated so that the projected lights are superposed one upon another on the surface.

2. A device according to claim 1, wherein said secondary light source forming means comprises a light source, reflecting means for reflecting the light from said light source and for forming an image of said light source, an optical integrator, and an imaging optical system for re-imaging the light source image, wherein said imaging optical system includes parallelizing means for transforming the light from the light source image into substantially parallel light, and collecting means for collecting the ring-like light from said deflecting member substantially into a ring-like shape upon said integrator.

3. A device according to claim 2, wherein said deflecting member is demountably mounted to the path of light to be received.

4. A device according to claim 3, wherein said imaging optical system comprises an optical system having a variable imaging magnification.

5. A device according to claim 3, further comprising means for moving said deflecting member in a direction intersecting with the optical axis of said imaging optical system.

6. A device according to claim 3, further comprising means for rotating said deflecting member about the optical axis.

7. A device according to claim 3, further comprising a second light deflecting member for reducing the angle of incidence of the ring-like light upon said integrator.

8. A device according to claim 7, wherein said second light deflecting member comprises a prism having a conical light deflecting surface.

9. A device according to claim 7, wherein said second light deflecting member comprises a field lens.

10. An exposure apparatus for exposing a substrate to a mask with light, said apparatus comprising:

secondary light source forming means having a deflecting member with a conical light deflecting surface for transforming received light into substantially ring-like light, said secondary light source forming means forming a ring-like secondary light source by using the ring-like light; and

an optical system for projecting divergent lights from portions of the secondary light source obliquely onto a surface to be illuminated so that the projected lights are superposed one upon another on the surface.

11. An apparatus according to claim 10, wherein said secondary light source forming means comprises a light source, reflecting means for reflecting the light from said light source and for forming an image of said light source, an optical integrator, and an imaging optical system for re-imaging the light source image, wherein said imaging optical system includes parallelizing means for transforming the light from the light source image into substantially parallel light, and collecting means for collecting the ring-like light from said deflecting member substantially into a ring-like shape upon integrator.

12. An apparatus according to claim 11, wherein said deflecting member is demountably mounted to the path of light to be received.

13. An apparatus according to claim 12, wherein said image optical system comprises an optical system having a variable imaging magnification.

14. An apparatus according to claim 12, further comprising means for moving said deflecting member in a direction intersecting with the optical axis of said imaging optical system.

15. An apparatus according to claim 14, further comprising means for rotating said deflecting member about the optical axis.

16. An apparatus according to claim 14, further comprising a second light deflecting member for reducing the angle on incidence of the ring-like light upon said integrator.

17. An apparatus according to claim 16, wherein said second light deflecting member comprises a prism having a conical light deflecting surface.

18. An apparatus according to claim 16, wherein said second light deflecting member comprises a field lens.

19. An apparatus according to claim 10, further comprising means for imaging a pattern of the mask onto the substrate.

20. A device manufacturing method including a step of exposing a workpiece to a mask, said method comprising the steps of:

projecting light onto a light deflecting surface of conical shape to produce substantially ring-like light;

forming a secondary light source by using the ring-like light;

projecting lights from portions of the secondary light source obliquely onto the mask so that the lights are superposed one upon another on the mask.

21. A method according to claim 20, wherein a pattern of the mask is imaged on the workpiece.

22. An illumination device, comprising:

a light source;

an optical integrator;

an imaging optical system for imaging said light source, said imaging optical system including (i) parallelizing means for transforming light from said light source into substantially parallel light, (ii) a deflecting member having a light deflecting surface of one of conical shape or pyramidal shape, for receiving the light from said parallelizing means, and (iii) light collecting means for collecting ring-like light or a plurality of lights from said deflecting member into a substantially ring-like shape or a plurality of light spots upon said optical integrator;

an optical system for projecting lights from portions of a secondary light source formed by said integrator obliquely upon a surface to be illuminated so that the lights are superposed one upon another on the surface; and

means for changing a positional relationship between an apex of said light deflecting surface and the optical axis.

23. A device according to claim 22, wherein said deflecting member is demountably mounted to the path of light from said light source.

24. A device according to claim 23, wherein said imaging optical system comprises an optical system having a variable imaging magnification.

25. A device according to claim 23, further comprising means for rotating said deflecting member about the optical axis.

26. A device to claim 23, further comprising a second light deflecting member for reducing the angle of incidence of the ring-like light or the plurality of lights upon said integrator.

27. A device according to claim 26, wherein said second light deflecting member comprises a prism having a conical light deflecting surface.

28. A device according to claim 26, wherein said second light deflecting member comprises a field lens.

29. An exposure apparatus for exposing a substrate to a mask with light, said apparatus comprising:

a light source;

an optical integrator;

an imaging optical system for imaging said light source, said imaging optical system including (i) parallelizing means for transforming light from said light source into substantially parallel light, (ii) a deflecting member having a light deflecting surface of one of conical shape or pyramidal shape, for receiving the light from said parallelizing means, and (iii) light collecting means for collecting ring-like light or a plurality of lights from said deflecting member into a substantially ring-like shape or a plurality of light spots upon said optical integrator;

an optical system for projecting lights from portions of a secondary light source formed by said integrator obliquely upon a surface to be illuminated so that the lights are superposed one upon another on the surface; and

means for changing a positional relationship between an apex of said light deflecting surface and the optical axis.

30. An apparatus according to claim 29, wherein said imaging optical system comprises first image forming means for reflecting light from said light source and for forming an image of said light source, and second image means for re-imaging the light source image, wherein said second image forming means includes said parallelizing means, said deflecting member and said collecting means.

31. An apparatus according to claim 29, wherein said deflecting member is demountably mounted to the path of light from said light source.

32. An apparatus according to claim 29, wherein said imaging optical system comprises an optical system having a variable imaging magnification.

33. An apparatus according to claim 29, further comprising means for rotating said deflecting member about the optical axis.

34. An apparatus according to claim 29, further comprising a second light deflecting member for reducing the angle of incidence of the ring-like light or the plurality of lights upon said integrator.

35. An apparatus according to claim 34, wherein said second light deflecting member comprises a prism having a conical light deflecting surface.

36. An apparatus according to claim 34, wherein said second light deflecting member comprises a field lens.

37. An apparatus according to claim 29, further comprising means for imaging a pattern of the mask onto the substrate.

38. A device manufacturing method including a step of exposing a workpiece to a mask with a light, said method comprising the steps of:

projecting light to a light deflecting surface of conical shape or pyramidal shape to form ring-like light or a plurality of lights;

forming a secondary light source by using the ring-like light or the plurality of lights;

wherein, in said projecting step and said secondary light source forming step, the positional relationship between an apex of the light deflecting surface and the optical axis is changed to provide the secondary light source of a desired intensity distribution; and

projecting divergent lights from portions of the secondary light source obliquely upon the mask so that the lights are superposed one upon another on the mask.

39. A method according to claim 38, wherein a pattern of the mask is imaged on the workpiece.

40. An illumination device, comprising:

a light source;

an optical integrator;

an imaging optical system for imaging said light source, said imaging optical system including (i) parallelizing means for transforming light from said light source into substantially parallel light, (ii) a first deflecting member having a light deflecting surface of one of conical shape or pyramidal shape, for receiving the light from said parallelizing means, and (iii) light collecting means for collecting ring-like light or a plurality of lights from said first deflecting member into a substantially ring-like shape or a plurality of light spots upon said optical integrator; and

an optical system for projecting lights from portions of a secondary light source formed by said integrator obliquely upon a surface to be illuminated so that the lights are superposed one upon another on the surface;

wherein said collecting means of said imaging optical system includes a second deflecting member effective to reduce the angle of incidence upon said integrator of the ring-like light or of the plurality of lights; and

wherein said first and second deflecting members are provided in a pair demountably mounted.

41. A device according to claim 40, wherein said imaging optical system comprises an optical system having a variable imaging magnification.

42. A device according to claim 40, further comprising means for moving said first deflecting member in a direction intersecting with the optical axis of said imaging optical system.

43. A device according to claim 40, further comprising means for rotating said first deflecting member about the optical axis.

44. A device according to claim 40, wherein each of said first and second deflecting members comprise a prism having a conical light deflecting surface.

45. A device according to claim 40, wherein each of said first and second deflecting members comprise a prism having a pyramidal light deflecting surface.

46. A device according to claim 40, wherein said second deflecting member comprises a field lens.

47. A device according to claim 40, wherein said imaging optical system comprises first image forming means for reflecting light from said light source and for forming an image of said light source, and second image forming means for re-imaging the light source image, wherein said second image forming means includes said parallelizing means, said deflecting member and said collecting means.

48. An exposure apparatus for exposing a substrate to a mask with light, said apparatus comprising:

a light source;

an optical integrator;

an imaging optical system for imaging said light source, said imaging optical system including (i) parallelizing means for transforming light from said light source into substantially parallel light, (ii) a first deflecting member having a light deflecting surface of one of conical shape or pyramidal shape, for receiving the light from said parallelizing means, and (iii) light collecting means for collecting ring-like light or a plurality of lights from said first deflecting member into a substantially ring-like shape or a plurality of light spots upon said optical integrator; and

an optical system for projecting lights from portions of a secondary light source formed by said integrator obliquely upon a surface to be illuminated so that the lights are superposed one upon another on the surface;

wherein said collecting means of said imaging optical system includes a second deflecting member effective to reduce the angle of incidence upon said integrator of the ring-like light or of the plurality of lights; and

wherein said first and second deflecting members are provided in a pair demountably mounted.

49. An apparatus according to claim 48, wherein said imaging optical system comprises an optical system having a variable imaging magnification.

50. An apparatus according to claim 48, further comprising means for moving said first deflecting member in a direction intersecting with the optical axis of said imaging optical system.

51. An apparatus according to claim 48, further comprising means for rotating said first deflecting member about the optical axis.

52. An apparatus according to claim 48, wherein each of said first and second deflecting members comprise a prism having a conical light deflecting surface.

53. An apparatus according to claim 48, wherein each of said first and second deflecting members comprise a prism having a pyramidal light deflecting surface.

54. An apparatus according to claim 48, wherein said second deflecting member comprises a field lens.

55. An apparatus according to claim 48, wherein said imaging optical system comprises first image forming means for reflecting light from said light source and for forming an image of said light source, and second image forming means for re-imaging the light source image, wherein said second image forming means includes said parallelizing means, said deflecting member and said collecting means.

56. An apparatus according to claim 48, further comprising means for imaging a pattern of the mask on the substrate.

57. A device manufacturing method including a step of exposing a workpiece to a mask, said method comprising the steps of:

projecting parallel light on a first deflecting surface of conical shape or pyramidal shape to produce ring-like light or a plurality of lights;

projecting the ring-like light or the plurality of lights to form a secondary light source;

wherein in said secondary light source forming step, the ring-like light or the plurality of lights are deflected by a second deflecting surface to reduce the angle of incidence thereof upon the plane; and

projecting divergent lights from portions of the secondary light source obliquely onto the mask so that the lights are superposed one upon another on the mask;

wherein the first and second deflecting surfaces are provided in a pair demountably mounted; and

wherein the parallel light can be projected to an approximately central portion of the plane, when the first and second deflecting surfaces are not present.

58. A method according to claim 57, wherein a pattern of the mask is imaged on the workpiece.

59. An illumination device, comprising:

a light source;

an imaging optical system for imaging said light source, said imaging optical system including (i) parallelizing means for transforming light from said light source into substantially parallel light, (ii) a deflecting member having a light deflecting surface of one of conical shape or pyramidal shape, for receiving the light from said parallelizing means, and (iii) light collecting means for collecting ring-like light or a plurality of lights from said deflecting member into a substantially ring-like shape or a plurality of light spots upon said optical integrator;

an optical system for projecting lights from portions of a secondary light source formed by said integrator obliquely upon a surface to be illuminated so that the lights are superposed one upon another on the surface; and

means for changing the positional relationship between an apex of said deflecting surface and the optical axis.

60. An illumination device, comprising:

a light source;

an imaging optical system for imaging said light source, said imaging optical system including (i) parallelizing means for transforming light from said light source into substantially parallel light, (ii) a first deflecting member having a light deflecting surface of one of conical shape or pyramidal shape, for receiving the light from said parallelizing means, and (iii) light collecting means for collecting ring-like light or a plurality of lights from said first deflecting member into a substantially ring-like shape or a plurality of light spots upon a plane; and

an optical system for projecting lights from portions of a secondary light source formed by the light from said first deflecting member, obliquely upon a surface to be illuminated so that the lights are superposed one upon another on the surface;

wherein said collecting means of said imaging optical system includes a second deflecting member effective to reduce the angle of incidence upon said plane of the light from said first deflecting surface; and

wherein said first and second deflecting members are provided in a pair demountably mounted.

FIELD OF THE INVENTION AND RELATED ART

This invention relates to an illumination device and a projection exposure apparatus using the same. More particularly, the invention is concerned with an illumination device usable in a microdevice manufacturing exposure apparatus (called a stepper) for illuminating a pattern formed on a reticle in a manner easily attaining high resolution. In another aspect, the invention is concerned with a projection exposure apparatus using such an illumination device.

Semiconductor device manufacturing technology has recently been advanced significantly and, along with this, the fine processing technique has been improved considerably. Particularly, the optical processing technique has pressed the fine processing into a submicron region, with the manufacture of a device of 1-megabit DRAM. A conventionally adopted method for improving the resolution is mainly to enlarge the numerical aperture (NA) of an optical system while fixing an exposure wavelength. Recently, however, it has been proposed and practiced to use an exposure wavelength of i-line in place of g-line, in an attempt to improve the resolution in accordance with an exposure method using an ultra-high pressure Hg lamp.

Along with the advancement of using g-line or i-line as the exposure wavelength, the resist process itself has been advanced. Such improvements in the optical system and in the process together have accomplished rapid advancement of optical lithography.

Generally it is known that the depth of focus of a stepper is in inverse proportion to the square of the NA. It means that enhancing the resolution into a submicron order necessarily results in a problem of decreased depth of focus.

In consideration of this problem, many proposals have been made to use shorter wavelengths, as represented by an excimer laser, for enhancement of the resolution. It is known that the effect of using a shorter wavelength is in inverse proportion to the wavelength, and the shorter the wavelength is, the deeper the depth of focus is.

On the other hand, independently of using light of shorter wavelength, many proposals have been made to use a phase shift mask (phase shift method), in an attempt to improve the resolution. According to this method, a mask of conventional type is locally provided with a thin film that imparts to light incident on it a phase shift of 180 deg. relative to the light incident on the remaining portion. An example has been proposed by Levenson of the IBM corporation. Here, if the wavelength is denoted by .lambda., the parameter is denoted by k.sub.1 and the numerical aperture is denoted by NA, then the resolution RP can be give by:

RP=k.sub.1 .lambda./NA

It is known that the parameter k.sub.1, whose practical range is usually taken as 0.7-0.8, can be improved to about 0.35 with this phase shift method.

There are many varieties of such a phase shift method, as referred to in a paper by Fukuda et al ("Nikkei Microdevices", July 1990, from page 108).

However, there remains many problems in practically using a phase shift mask of spatial frequency modulation type to improve the resolution. Examples are as follows:

(1) Unestablished technique for forming a phase shift film;

(2) Unestablished CAD technique optimized to a phase shift film;

(3) Existence of a pattern to which no phase shift film can be put;

(4) Necessity of using a negative type resist (in relation to problem (3); and

(5) Unestablished technique for inspection and correction.

Under these circumstances, the phase shift mask method cannot be easily practiced in the semiconductor device manufacturing processes.

An exposure method and apparatus which attains enhanced resolution through an appropriately structured illumination device, has been proposed in Japanese patent application No. 28631/1991, filed in Japan on Feb. 22, 1991, in the name of the assignee of the subject application.

In this exposure method and apparatus, such an oblique projection illumination system is adopted wherein particular attention is paid to a high spatial frequency region around a k.sub.1 factor of 0.5. This illumination system assures a deep depth of focus in the high spatial frequency region.

SUMMARY OF THE INVENTION

Practical semiconductor device manufacturing processes include on one hand a process wherein high resolution of a pattern is required and, on the other hand, a process wherein a not so high resolution of a pattern is required. Thus, what is desired currently is a projection exposure apparatus which can meet the requirement of various resolution performances to be satisfied in various processes.

It is accordingly an object of the present invention to provide a variable or adaptable illumination device or a projection exposure apparatus using the same, by which a suitable illumination method appropriate to the resolution actually required can be selectively assured without decreasing the efficiency of utilization of light.

In accordance with an aspect of the present invention, there is provided an illumination device in which a light emitting portion is disposed in the neighborhood of a first focal point of an elliptical mirror. By using the light from the light emitting portion and through the elliptical mirror, an image of the light emitting portion is formed in the neighborhood of a second focal point of the elliptical mirror. Light from the image of the light emitting portion is projected through an optical integrator having a plurality of small lenses disposed two-dimensionally to illuminate a surface to be illuminated. An optical device is disposed demountably out of the light path, between the elliptical mirror and the integrator, to deflect the light in a predetermined direction, to thereby change the light intensity distribution at the light entrance surface of the integrator.

In accordance with another aspect of the present invention, there is provided an illumination device in which a light emitting portion is disposed in the neighborhood of a first focal point of an elliptical mirror. By using the light from the light emitting portion and through the elliptical mirror, an image of the light emitting portion is formed in the neighborhood of a second focal point of the elliptical mirror. This image is imaged again by an imaging system on the light entrance surface of an optical integrator having a plurality of small lenses disposed two-dimensionally, and a surface to be illuminated is illuminated with the light from the exit surface of the integrator. An optical device is disposed demountably out of the light path, adjacent to the pupil plane of the imaging system, to deflect the light in a predetermined direction, to thereby change the light intensity distribution at the light entrance surface of the integrator.

In accordance with a further aspect of the present invention, there is provided an illumination device in which light from a light source is projected through an optical integrator having small lenses disposed two-dimensionally to illuminate the surface to be illuminated. Between the light source and the integrator, an optical device for deflecting light in a predetermined direction is demountably inserted to the light path, to thereby change the light intensity distribution at the entrance surface of the integrator.

In accordance with a further aspect of the invention, there is provided an illumination device in which a light emitting portion is disposed in the neighborhood of a first focal point of an elliptical mirror. By using the light from the light emitting portion and through the elliptical mirror, an image of the light emitting portion is formed in the neighborhood of a second focal point of the elliptical mirror. Light from the image of the light emitting portion is projected through an optical integrator having a plurality of small lenses disposed two-dimensionally to illuminate a surface to be illuminated. An optical device including at least two prism members is disposed demountably out of the light path, between the elliptical mirror and the integrator, to deflect the light in a predetermined direction, so as to allow selection of a first state in which a light intensity distribution, of rotationally symmetric, having a higher intensity at its central portion than at the peripheral portion is defined at the entrance surface of the integrator and a second state in which the light intensity distribution having a higher intensity at the peripheral portion than at the central portion is defined at the entrance surface of the integrator.

In another aspect, the invention provides a method of manufacturing microdevices such as semiconductor memories, liquid crystal panels, magnetic heads or CCDs, for example, using an illumination device such as above.

In a further aspect, the invention provides an exposure apparatus for manufacture of microd