Surface height detecting apparatus and exposure apparatus using the same

• US 6,479,832 B1
• Filed: 03/15/1999
• Issued: 11/12/2002
• Est. Priority Date: 07/22/1996
• Status: Expired due to Term

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Hori, Kazuhiko, Naraki, Tsuyoshi
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US09/267,682
• Time in Patent Office: 1,338 Days
• Field of Search: 250/201.2, 250/201.5, 250/201.4, 250/548, 250/559.29, 250/559.3, 250/559.4, 250/559.27, 356/630, 356/601, 356/609, 356/610, 356/509, 356/510, 356/511, 356/516
• US Class Current: 250/559.3
• CPC Class Codes: G03F 9/7026 Focusing

Abstract

An illumination device emits detection light toward the surface of a substrate from an oblique direction with respect to the substrate. The detection light is shaped into a slit beam by an optical shaper. An alteration device changes the width of the slit beam by controlling the optical shaper. The slit beam strikes the surface of the substrate through an optical element. The slit beam reflected from the surface of the substrate is oscillated along the width direction of the slit by a controlled oscillation mirror. A detector detects the surface height of the substrate based on the oscillating slit beam.

Claims

1. A surface position detection apparatus for detecting a surface position of a substrate, the apparatus comprising:

an illumination device that emits detection light along a light path toward a substrate surface from an oblique direction with respect to the substrate surface;

an optical shaper disposed in the light path downstream from the illumination device, the optical shaper shaping the detection light into a slit-like shape to generate a slit-like light beam;

an alteration device communicating with the optical shaper and altering only a width of the slit-like light beam by controlling the optical shaper;

an optical element disposed in the light path downstream from the optical shaper, the optical element guiding the slit-like light beam onto the substrate surface; and

a detector disposed in the light path and receiving the slit-like light beam reflected from the substrate surface.

2. The surface position detection apparatus as claimed in claim 1, wherein the width of the slit-like light beam is determined such that the slit-like light beam reflected from the top surface of the substrate is separated from the slit-like light beam reflected from the bottom surface of the substrate.

3. The surface position detection apparatus as claimed in claim 1, further comprising:

an oscillation controller that oscillates the slit-like light beam reflected from the substrate surface along the width direction of the slit-like light beam to generate an oscillating slit-like light beam; and

an amplitude controller that controls the amplitude of the oscillation of the slit-like light beam oscillated by the oscillation controller according to the width of the slit-like light beam that has been altered by the alteration device, wherein the detector receives the oscillating slit-like light beam.

4. The surface position detection apparatus as claimed in claim 1, further comprising a memory connected to the alteration device, the memory supplying information including a thickness of the substrate to the alteration device, wherein the alteration device determines the width of the slit-like light beam according to the thickness of the substrate included in the information supplied from the memory.

5. The surface position detection apparatus as claimed in claim 4, wherein the alteration device increases the width of the slit-like light beam along the light path as the thickness of the substrate increases.

6. The surface position detection apparatus as claimed in claim 1, further comprising a controller connected to the alteration device, the controller having at least a first operating mode to detect the surface position of the substrate roughly and a second operating mode to detect the surface position of the substrate precisely, wherein the alteration device increases the width of the slit-like light beam when the controller selects the first operating mode, and decreases the width of the slit-like light beam when the controller selects the second operating mode.

7. The surface position detection apparatus as claimed in claim 1, further comprising a memory connected to the alteration device, the memory supplying information including a material of the substrate to the alteration device, wherein the alteration device determines the width of the slit-like light beam according to the material of the substrate included in the information supplied from the memory.

8. The surface position detection apparatus as claimed in claim 1, further comprising a slit plate positioned at an image-forming spot of the slit-like light beam reflected by the substrate surface, wherein the detector receives the slit-like light beam that has passed through the slit plate.

9. The surface position detection apparatus as claimed in claim 8, wherein the slit plate comprises a liquid crystal device having a slit-like transparent area in a center thereof, and wherein the apparatus further comprises a liquid crystal controller communicating with the liquid crystal device and controlling a voltage applied to liquid cell electrodes surrounding the slit-like transparent area.

10. The surface position detection apparatus as claimed in claim 1, wherein the optical shaper comprises a slit plate disposed in the light path adjacent the illumination device.

11. The surface position detection apparatus as claimed in claim 10, wherein the slit plate comprises a liquid crystal device having a slit-like transparent area in a center thereof, and wherein the alteration device comprises a liquid crystal controller communicating with the liquid crystal device and controlling a voltage applied to liquid cell electrodes surrounding the slit-like transparent area.

12. The surface position detection apparatus as claimed in claim 10, wherein the slit plate comprises a variable slit-like transparent area in a center thereof, the variable slit-like transparent area being controlled by the alteration device.

13. The surface position detection apparatus as claimed in claim 1, further comprising a movable plate glass disposed in the light path between the oscillation controller and the detector, the movable plate glass shifting an image-forming position of the oscillating slit-like light beam.

14. The surface position detection apparatus as claimed in claim 1, wherein the detector comprises:

a light-receiving element receiving the oscillating slit-like light beam and converting the oscillating slit-like light beam into an electrical signal; and

a phase synchronous demodulator (PSD) receiving the electrical signal from the light-receiving element.

15. An exposure apparatus comprising:

an exposure light source that emits exposure light along an optical axis to a mask to illuminate a pattern formed on the mask;

a projection optical system disposed along the optical axis and receiving the exposure light source, the projection optical system transferring an image of the pattern onto a surface of a photosensitive substrate;

an illumination device that emits detection light along a light path toward the surface of the photosensitive substrate from an oblique direction with respect to the photosensitive substrate surface;

an optical shaper disposed in the light path downstream from the illumination device, the optical shaper shaping the detection light into a slit-like shape to generate a slit-like light beam;

an alteration device communicating with the optical shaper and altering only a width of the slit-like light beam by controlling the optical shaper;

an optical element disposed in the light path downstream form the optical shaper, the optical element guiding the slit-like light beam onto the surface of the photosensitive substrate;

a detector disposed in the light path and receiving the slit-like light beam reflected from the substrate surface; and

a driving unit communicating with the detector and supporting the photosensitive substrate along the optical axis of the projection optical system based on the detecting result of the detector so that the surface of the photosensitive substrate comes into alignment with a focusing position of the exposure light.

16. The exposure apparatus as claimed in claim 15, wherein the width of the slit-like light beam is determined such that the slit-like light beam reflected from the top surface of the photosensitive substrate is separated from the slit-like light beam reflected from the bottom surface of the photosensitive substrate.

17. The exposure apparatus as claimed in claim 15, further comprising:

an oscillation controller that oscillates the slit-like light beam reflected from the surface of the photosensitive substrate along the width direction of the slit-like light beam to generate an oscillating slit-like light beam; and

an amplitude controller that controls the amplitude of the oscillation of the slit-like light beam oscillated by the oscillation controller according to the width of the slit-like light beam that has been altered by the alteration device, wherein the detector receives the oscillating slit-like light beam.

18. The exposure apparatus as claimed in claim 15, further comprising a memory connected to the alteration device, the memory storing information relating to the photosensitive substrate.

19. The exposure apparatus as claimed in claim 18, wherein

the information comprises at least one of a thickness of the photosensitive substrate and a material of the substrate, and

the alteration device determines the width of the slit-like light beam according to at least one of the thickness and the material comprised in the information of the memory.

20. The exposure apparatus as claimed in claim 15, further comprising a master controller connected to the alteration device, the master controller having at least a first operating mode to detect the surface position of the photosensitive substrate roughly and a second operating mode to detect the surface position of the photosensitive substrate precisely, wherein the alteration device increases the width of the slit-like light beam when the master controller selects the first operating mode, and decreases the width of the slit-like light beam when the master controller selects the second operating mode.

21. The exposure apparatus as claimed in claim 15, further comprising:

a master controller connected to the alteration device, the master controller controlling the alteration device; and

an arithmetic operation unit connected to the master controller, the arithmetic operation unit determining an optimum width of the slit-like light beam based on the thickness and material of the photosensitive substrate.

22. The exposure apparatus as claimed in claim 15, wherein

the arithmetic operation unit determines an optimum amplitude of the oscillation of the slit-like light beam oscillated by the oscillation controller based on the width of the slit-like light beam, and

the master controller controls the oscillation controller based on the optimum amplitude of the oscillation.

23. The exposure apparatus as claimed in claim 15, wherein the detector comprises:

a light-receiving element receiving the oscillating slit-like light beam and converting the oscillating slit-like light beam into an electrical signal; and

a phase synchronous demodulator (PSD) receiving the electrical signal from the light-receiving element.

24. The exposure apparatus as claimed in claim 23, wherein

the PSD outputs the offset signal that shows a distance between the surface of the photosensitive substrate and an image-forming plane of the projection optical system, and

the master controller controls the driving unit based on the offset signal.

25. An auto focus (AF) sensor system for determining a surface position of a substrate, the AF sensor system comprising:

a light-transmitting device that emits detection light along a light path toward a surface of the substrate from an oblique direction with respect to the surface, the light-transmitting device including structure that shapes the detection light into a slit-like light beam;

a light receiving device disposed in the light path and receiving the slit-like light beam;

a memory having information that includes at least one of a thickness and a material of the substrate; and

a controller communicating with the light-transmitting device, the light receiving device, and the memory, the controller controlling a width of the slit-like light beam in accordance with the thickness and the material of the substrate.

26. The AF sensor system as claimed in claim 25, wherein the width of the slit-like light beam is determinded such that the slit-like light beam reflected from the top surface of the substrate is separated from the slit-like light beam reflected from the bottom surface of the substrate.

27. The AF sensor system as claimed in claim 25, wherein

the light receiving device comprises an oscillating device that oscillates the slit-like beam, and

the controller controls the amplitude of the oscillation of the slit-like beam via the oscillating device.

28. The AF sensor system as claimed in claim 25, wherein the structure that shapes the detection light comprises a slit plate disposed in the light path.

29. The AF sensor system as claimed in claim 28, wherein the slit plate comprises a liquid crystal device having a slit-like transparent area in a center thereof, and wherein the controller comprises a liquid crystal controller communicating with the liquid crystal device and controlling a voltage applied to liquid cell electrodes surrounding the slit-like transparent area.

30. The AF sensor system as claimed in claim 28, wherein the slit plate comprises a variable slit-like transparent area in a center thereof, the variable slit-like transparent area being controlled by the controller based on a desired width of the slit-like light beam determined by the controller utilizing the information of the memory.

34. The exposure method as claimed in claim 25, further comprising prior to step (a) the step of (e) calibrating the AF sensor system.

35. The exposure method as claimed in claim 34, further comprising after step (b) the steps of shaping the detection light beam into a slit-like light beam and (f) controlling a width of the slit-like light beam according to the optimum width that is set based on at least one of the thickness and the material of the substrate.

36. The exposure method as claimed in claim 35, wherein step (e) is practiced by (e1) broadening the width of the slit-like light beam to a width wider than the optimum width, (e2) calculating a first surface position of the substrate by utilizing the slit-like light beam with the width wider than the optimum width, and (e3) positioning the substrate according to the first surface position.

37. The exposure method as claimed in claim 36, further comprising after steps (el)-(e3) the step of narrowing the width of the slit-like light beam to the optimum width and performing steps (b)-(d).

38. The exposure method as claimed in claim 37, further comprising after step (e) the step of (f) triggering an exposure shot from the exposure light source to expose the substrate.

39. The exposure method as claimed in claim 38, further comprising after step (f) the step of (g) replacing the substrate with a second substrate and positioning the second substrate in the first surface position.

31. An exposure method utilizing an exposure apparatus including an auto focus AF) sensor system, an exposure light source for emitting exposure light along an optical axis to a mask to illuminate a pattern formed on the mask, and a projection optical system disposed along the optical axis and receiving the exposure light from the exposure light source, the projection optical system transferring an image of the pattern onto a surface of a substrate, the method comprising:

(a) determining an optimum width of a detection light beam according to at least one of a thickness and a material of the substrate;

(b) emitting the detection light beam along a light path toward the surface of the substrate from an oblique direction with respect to the surface;

(c) receiving the detection light beam reflected from the surface of the substrate and calculating a surface position of the substrate; and

(d) controlling a position of the substrate with respect to the direction substantially parallel to the optical axis according to the surface position of the substrate.

32. The exposure method as claimed in claim 31, wherein the width of the detection light beam is determined such that the detection light beam reflected from the top surface of the substrate is separated from the detection light beam reflected from the bottom surface of the substrate.

33. The exposure method as claimed in claim 31, further comprising after step (d) the step of triggering an exposure shot from the exposure light source to expose the substrate.

40. The exposure method as claimed in claim 31, further comprising after step (b) the steps of (h) shaping the detection light beam into a slit-like light beam and (i) controlling a width of the slit-like light beam according to the optimum width that is set based on at least one of the thickness and the material of the substrate.

41. The exposure method as claimed in claim 40, further comprising (j) increasing the width of the slit-like light beam when positioning the substrate a first time and decreasing the width of the slit-like light beam when positioning the substrate after the first time.

42. The exposure method as claimed in claim 31, wherein step (a) is practiced by increasing the optimum width as the thickness of the substrate increases.

43. The exposure method as claimed in claim 31, further comprising after step (b) the step of (k) oscillating the detection light beam reflected from the surface of the substrate with a predetermined amplitude that is set according to the width of the detection light beam.