Plane positioning apparatus

• US 6,400,456 B1
• Filed: 10/27/2000
• Issued: 06/04/2002
• Est. Priority Date: 09/14/1993
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Miyachi, Takashi
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Lee, Andrew H.
• Application Number:
  US09/697,357
• Time in Patent Office: 585 Days
• Field of Search: 356/399, 356/400, 356/401, 356/375, 355/43, 355/53, 355/56, 355/55, 355/67, 355/77, 430/30, 438/16
• US Class Current: 356/399
• CPC Class Codes: G03F 7/70358 Scanning exposure, i.e. relative movement of patterned beam and workpiece during imaging
• CPC Class Codes: G03F 9/7003 Alignment type or strategy, e.g. leveling, global alignment
• CPC Class Codes: G03F 9/7026 Focusing
• CPC Class Codes: G03F 9/7034 Leveling
• CPC Class Codes: G03F 9/7092 Signal processing

Abstract

It is intended to perform optimum autofocusing and autoleveling control in a scanning exposure apparatus.

A focus position ΔZ (focus position of a curved surface 46 or 47) in a region 34 surrounding a slit exposure region 16A or 16 is measured on the exposure plane of a wafer. For the narrow exposure region 16A, an approximate plane of a partial curved surface 46a in the exposure region 16A is calculated by using only data on the focus position of the partial curved surface 46a. For the normal exposure region 16, an approximate plane of a partial curved surface 47a in the exposure region 16 is calculated by using only data on the focus position of the partial curved surface 47a. These approximate planes are matched with an imaging plane by an optical projection system. A curved surface 51 is obtained by filtering the curved surface 50 in the region 34 with a low-pass filter which has an amplitude transmission characteristic ¦H(jω)¦ on a spatial frequency range. The average plane of the curved surface 51 is matched with the imaging plane of the optical projection system. Cutoff spatial frequencies ω_X and ω_Y of the low-pass filter are set to values inversely proportional to the width W_O of the exposure region 16 in the scanning direction and the height H_O in the nonscanning direction.

Claims

1. In a plane positioning apparatus installed on a scanning exposure apparatus, which comprises a mask stage for scanning a mask formed with a transfer pattern in a predetermined direction in respect to a radiating region with a predetermined variable shape, and a substrate stage for scanning a photosensitive substrate in a predetermined direction in synchronization with said mask stage, and which sequentially exposes the pattern of said mask onto said substrate, said plane positioning apparatus being for aligning the exposure plane of said substrate with a predetermined reference plane, and comprising:

a plane positioning means installed on said substrate stage for aligning a predetermined approximate plane of the exposure plane of said substrate with said predetermined reference plane;

a height detection means for detecting height information of the exposure plane of said substrate at a plurality of measurement points in a measurement region before an exposure region of the pattern of said mask with respect to the scanning direction of said substrate; and

an approximate plane calculation means for calculating said approximate plane of the exposure plane of said substrate by using a plurality of the height information on the exposure plane of said substrate from said height detection means;

wherein said plurality of the height information is selected in accordance with a variation in shape of said exposure region, and the shape of the exposure region varies according to said variable radiating region during the scanning exposure; and

wherein the calculated approximate plane being aligned with said predetermined reference plane by said plane positioning means.

2. A plane positioning apparatus according to claim 1, wherein said approximate plane calculation means includes a filter means which has low-pass characteristics filtering the height information of said plurality of measurement points detected by said height detection means, an approximate plane of the exposure plane of said substrate being calculated from information after filtering the plurality of the height information on the exposure plane of said substrate measured in the variable exposure region of the pattern of said mask with said filter means;

cutoff spatial frequencies in an amplitude transmission characteristic of said filter means in the scanning direction of said substrate and in a nonscanning direction normal to the scanning direction of said substrate being set in proportion to inverse numbers of a width of the exposure region of the pattern of said mask in the scanning direction of said substrate and the width in the nonscanning direction of said substrate;

the calculated approximate plane being aligned with said predetermined reference plane by said plane positioning means.

3. A plane positioning apparatus according to claim 1, wherein an optical projection system with a projection magnification β

is provided between said mask and said substrate, said mask stage scanning at a speed of V_R in a predetermined direction in a plane normal to the axis of said optical projection system, said substrate stage scanning at a speed of β

·

V_R in a direction opposite to said predetermined direction in a plane normal to said axis.

4. In a plane positioning apparatus installed on a scanning exposure apparatus, which comprises a mask stage for scanning a mask formed with a transfer pattern in a predetermined direction in respect to a radiating region with a predetermined variable shape, and a substrate stage for scanning a photosensitive substrate in a predetermined direction in synchronization with said mask stage, and which sequentially exposes the pattern of said mask onto said substrate, said plane positioning apparatus being for aligning the exposure plane of said substrate with a predetermined reference plane, and comprising:

a drive device installed on said substrate stage for aligning a predetermined approximate plane of the exposure plane of said substrate with said predetermined reference plane at a same level and in parallel to said reference plane;

a sensor for detecting height information of the exposure plane of said substrate at a plurality of measurement points in a measurement region before an exposure region of the pattern of said mask with respect to the scanning direction of said substrate; and

a computer for calculating said predetermined approximate plane of the exposure plane of said substrate by using a plurality of the height information on the exposure plane of said substrate from said sensor, wherein said plurality of the height information is selected in accordance with a variation in a shape of said exposure region, and the shape of the exposure region varies according to said variable radiating region during the scanning exposure.

5. A scanning exposure apparatus comprising:

an illumination system for radiating illumination light on a mask through an opening of a variable field diaphragm positioned on a plane substantially conjugate with a pattern plane of the mask;

an optical projection system for projecting a pattern formed on said mask onto a photosensitive substrate;

a movable member for moving, during scanning exposure, said mask and said substrate in a direction substantially normal to an axis of said optical projection system;

a drive member for changing a width of the opening of said variable field diaphragm in accordance with the movement of said mask;

a sensor system having a plurality of measurement points in a region before an exposure region of the pattern of said mask with respect to the direction of movement of said substrate, and detecting position information of a surface of said substrate in a direction of the optical axis of said optical projection system at each of said plurality of measurement points;

a calculator for, during said scanning exposure, calculating an approximate plane of the surface of said substrate based on the position information in the exposure region detected by the sensor system, the shape of the exposure region varying according to a change in a width of the opening of said variable field diaphragm and the approximate plane being calculated in accordance with the change in the shape of the exposure region; and

a device for moving said substrate and an imaging plane of said optical projection system relative to each other so as to substantially match said approximate plane calculated with said imaging plane.

6. A plane positioning apparatus according to claim 5, wherein said calculator includes a filter member which has low-pass characteristics filtering the height information of said plurality of measurement points detected by said sensor system, an approximate plane of the exposure plane of said substrate being calculated from information on the exposure plane of said substrate measured in the variable exposure region of the pattern of said mask with said filter member.

7. A scanning projection exposure method wherein an image of a pattern on a mask is transferred onto a substrate through an optical projection system while said mask and said substrate move in synchronization with one another, said scanning exposure method comprising:

changing, during scanning exposure, a shape of an exposure region on said substrate;

selecting a part of position data, in a direction perpendicular to an image of said optical projection system, of a plurality of positions on a surface of said substrate during scanning exposure in accordance with the change in shape of said exposure region;

calculating an approximate plane of said surface of the substrate based on said selected position data; and

moving said substrate and said image plane relatively with respect to one another to adjust a positional relationship between said calculated approximate plane and said image plane of the optical projection system.

8. A scanning projection exposure method according to claim 7,

wherein said shape of the exposure region is defined in a rectangle having a long side in a direction substantially perpendicular to a moving direction of said substrate, and

the change of said shape of the exposure region includes a change of a width of said rectangle in said direction of movement of said substrate.

9. A scanning projection exposure method according to claim 7, further comprising:

measuring said position data of the plurality of positions on said surface of the substrate.

10. A scanning projection exposure method wherein an image of a pattern on a mask is transferred onto a substrate through an optical projection system while said mask and said substrate move in synchronization with one another, said scanning exposure method comprising:

altering a condition for selecting a part of position data, in a direction perpendicular to an image plane of said optical projection system, of a plurality of positions on a surface of said substrate during scanning exposure in accordance with change in a shape of an exposure region on said substrate, wherein the shape of said exposure region changes during the scanning exposure; and

adjusting a positional relationship between said substrate and said image plane based on said selected position data.

11. A scanning projection exposure apparatus wherein a mask and a substrate are moved synchronously, said apparatus comprising:

a variable field diaphragm arranged on a plane substantially conjugate with a pattern plane of the mask;

an optical projection system disposed between said mask and the substrate, which projects an image of a pattern formed on said mask onto the substrate;

a driving system, functionally connected with said variable field diaphragm, which changes a shape of an opening of said variable field diaphragm during scanning exposure;

a calculator, functionally connected with said driving system, which calculates an approximate plane of a surface of said substrate based on a part of position data at a plurality of positions on said surface of the substrate in a direction perpendicular to an image plane of said optical projection system, the part of position data being selected in accordance with said change in the opening shape of said variable field diaphragm during scanning exposure; and

an adjusting system, functionally connected with the calculator, which adjusts a positional relationship between said substrate and said image plane based on said calculated approximate plane.

12. A scanning projection exposure apparatus according to claim 11, further comprising:

a sensor, functionally connected with said calculator, which has a plurality of measurement points in a region apart from an exposure region on the substrate with respect to a direction of movement of said substrate and which is used for obtaining said position data.

13. A scanning projection exposure apparatus according to claim 11, further comprising:

a memory, functionally connected with said calculator, which memorizes said position data perpendicular to said image plane of said projection system.

14. A scanning projection exposure apparatus according to claim 11, wherein said calculator calculates an inclination of said approximate plane and a distance along an optical axis of said optical projection system between said approximate plane and said image plane of said optical projection system.

15. A scanning projection exposure apparatus in which a mask and a substrate are moved synchronously, the apparatus comprising:

an optical projection system disposed between said mask and said substrate, which projects an image of a pattern formed on said mask onto said substrate;

a sensor system which has measurement points in a region before an exposure region on the substrate with respect to a direction of movement of said substrate, wherein said sensor system measures position data, in a direction perpendicular to an image plane of said optical projection system, of a surface of said substrate at each point of said measurement points; and

an adjustment system, functionally connected with said sensor system, which adjusts a positional relationship between said substrate and said image plane of said optical projection system based on a part of position data measured by said sensor system during scanning exposure, wherein the part of position data are selected in accordance with change in a shape of said exposure region.

16. A scanning projection exposure apparatus wherein a mask and a substrate are moved synchronously, the apparatus comprising:

an optical projection system disposed between said mask and said substrate, which projects an image of a pattern formed on said mask onto said substrate;

a sensor system which has measurement points to measure position data, in a direction perpendicular to an image plane of said optical projection system, of a surface of said substrate during scanning exposure; and

a filtering system, functionally connected with said sensor, which has a filtering characteristic based on a shape of an exposure region and which filters the position data measured by said sensor system, said exposure region on said substrate corresponding to a radiation region of an exposure beam on said mask; and

an adjustment system, functionally connected with said filtering system, which adjusts a positional relationship between said substrate and said image plane of said optical projection system based on the filtered position data during scanning exposure.

17. A scanning projection exposure apparatus according to claim 16, wherein said shape of said exposure region changes during scanning exposure.

18. A scanning projection exposure apparatus according to claim 16, wherein said exposure region is defined in a rectangle having a long side in a direction substantially perpendicular to a moving direction of said substrate and a short side in the moving direction of said substrate, and said filtering characteristic of said filtering system is based on a length of the long side and a length of the short side of said rectangle.

19. A scanning exposure method wherein an image of a pattern on a mask is projected onto a substrate through an optical projection system while said mask and said substrate move in synchronization with one another, said scanning exposure method comprising:

obtaining position data, in a direction perpendicular to an image plane formed by said optical projection system, of a surface of said substrate at each of a plurality of measurement points;

filtering said obtained position data by using a filter system having a filtering characteristic defined based on a shape of an exposure region, wherein said exposure region on said substrate corresponds to a radiation region of an exposure beam on said mask; and

adjusting a positional relationship between the substrate and said image plane of said optical projection system based on the filtered position data.

20. A scanning exposure method wherein an image of a pattern formed on a mask is projected onto a substrate through an optical projection system, said method comprising:

detecting, during scanning exposure, position data in an optically axial direction of said optical projection system at a plurality of positions on a surface of said substrate;

selecting, during the scanning exposure, position data in accordance with a change in shape of an exposure region out of said detected position data; and

moving, during the scanning exposure, said substrate and an imaging plane of said optical projection system with respect to one another based on the selected position data.

21. A scanning method according to claim 20 wherein said substrate is moved relative to the exposure region during the scanning exposure and wherein the position data in the exposure region are selected sequentially during the scanning exposure.

22. A scanning exposure method according to claim 21, wherein an approximate plane in the exposure region is calculated based on the selected position data.

23. A scanning exposure apparatus comprising:

a beam source which emits an exposure beam;

an optical projection system which projects an image of a pattern of a mask onto a substrate, said optical projection system being disposed between said mask and said substrate;

a variable field diaphragm arranged between said beam source and said substrate, wherein a shape of an exposure region on said substrate changes in accordance with changes in a shape of an opening of said variable field diaphragm during scanning exposure;

a sensor system which obtains position data in an optically axial direction of said optical projection system of a surface of said substrate at a plurality of measurement points; and

an adjustment system which selects, during the scanning exposure, position data in accordance with the change in the shape of said exposure region out of the position data obtained by said sensor system and which moves said substrate and an imaging plane of said optical projection system relatively with respect to one another based on the selected position data, said adjustment system being associated with said variable field diaphragm and said sensor system.

24. A scanning exposure method for exposing a substrate with an image of a pattern of a mask through an optical projection system, the method comprising:

measuring, during scanning exposure, a position on a surface of said substrate in an optically axial direction of said optical projection system at a plurality of measurement points related to an exposure region on said substrate, the exposure region on said substrate corresponding to an illumination region of an exposure beam on said mask; and

filtering a signal obtained by measuring the position by using a filter having a transmission characteristic which has a predetermined relationship with the shape of said exposure region; and

adjusting a positional relationship between said substrate and an imaging plane of said optical projection system based on the signal obtained after said filtering.

25. A scanning exposure apparatus comprising:

an optical projection system which projects an image of a pattern of a mask onto a substrate, said optical projection system disposed between said mask and said substrate;

a sensor system which measures a position in an optically axial direction of said optical projection system on an exposure plane of said substrate at a plurality of measurement points related to an exposure region on said substrate, the exposure region on said substrate corresponding to an illumination region of an exposure beam on said mask; and

a filtering system which filters a signal from said sensor system, said filtering system having a transmission characteristic which has a predetermined relationship with the shape of said exposure region.

26. An exposure method in which a substrate is exposed, the method comprising:

providing said substrate;

exposing said substrate by moving a mask and said substrate synchronously, wherein a shape of an exposure region on said substrate changes during the exposure;

obtaining, in accordance with the change in shape of the exposure region on said substrate, positional information on a surface of said substrate placed in said exposure region during the exposure; and

adjusting a positional relationship between an image plane and an exposure surface of said substrate on the basis of the obtained information.

27. An exposure method according to claim 26, further comprising:

measuring positions of the surface of said substrate in a direction substantially perpendicular to the surface at each of a plurality of measurement points to obtain said information on the surface.

28. An exposure method according to claim 26, further comprising:

providing a mask on which a pattern to be transferred to said substrate is formed;

changing a shape of an illuminating region on said mask during the exposure, wherein said shape of the exposure region changes according to said shape of the illuminating region.

29. An exposure method according to claim 27, further comprising:

selecting, in accordance with the change of the shape of the exposure region, a part of position data obtained by the measurement at the measurement points.

30. An exposure method according to claim 26, further comprising:

moving said substrate, during the exposure, relative to the exposure region.

31. An exposure method according to claim 27, wherein said measurement points are arranged outside the exposure region on said substrate.

32. An exposure method according to claim 27, wherein said measurement points are disposed before said exposure region in a moving direction of said substrate.

33. An exposure method according to claim 26, wherein said obtained information on the surface includes information about an inclination of the surface of the substrate.

34. An exposure method according to claim 27, wherein said plurality of measurement points are included in one of two groups of measurement points respectively arranged in the opposite sides of said exposure region with respect to the direction parallel to the movement direction of the substrate.

35. An exposure method according to claim 34, wherein said one group of measurement points is chosen according to the movement direction of the substrate.

43. An exposure method according to claim 28, wherein the shape of the illuminating region on said mask is defined by using a variable field diaphragm, the variable field diaphragm having four blades to define a width of the illuminating region in a scanning direction of the mask and in a direction perpendicular to the scanning direction.

44. An exposure method according to claim 43, further comprising:

measuring positions of the surface of said substrate in a direction substantially perpendicular to the surface at each of a plurality of measurement points to obtain said positional information on the surface.

45. An exposure method according to claim 44, further comprising:

selecting, in accordance with the change of the shape of the exposure region, a part of position data obtained by the measurement at the measurement points.

46. An exposure method according to claim 44, wherein the plurality of measurement points are arranged outside the exposure region.

36. A scanning exposure apparatus in which a mask and a substrate are moved synchronously to expose the substrate with a pattern formed on the mask, the apparatus comprising:

an irradiation system, disposed along a path of an exposure beam which directs the exposure beam to an exposure region, wherein the substrate is moved relative to the exposure region during exposure;

a variable field diaphragm, disposed in the irradiation system, which defines the exposure region, wherein a shape of the exposure region changes during the exposure;

a sensor which detects focussing information of the substrate at measurement points during the exposure; and

an adjustment system, functionally connected to the variable field diaphragm and the sensor, which adjusts a positional relationship between an image surface and the substrate during the exposure, based on the shape of the exposure region and the detected focussing information.

37. A scanning exposure apparatus according to claim 36, further comprising an interferometer system which measures positional information of the substrate in a scanning direction during the exposure, and

wherein a signal from the sensor is sampled on the basis of a signal from the interferometer system during the exposure.

38. A scanning exposure apparatus according to claim 36, wherein the exposure region is defined in a rectangle and the measurement points of the sensor are arranged along a long side of the rectangle exposure region.

39. A scanning exposure apparatus according to claim 38, wherein the sensor has measurement points outside of the exposure region.

40. A scanning exposure apparatus according to claim 39, wherein the sensor has measurement points inside of the exposure region.

41. A scanning exposure apparatus according to claim 38, wherein the adjustment system adjusts the positional relationship based on the focussing information corresponding to a surface of the substrate within the exposure region during the exposure.

42. A scanning exposure apparatus according to claim 41, wherein the adjustment system sequentially calculates, during the exposure, an approximate plane of the surface of the substrate within the exposure region to adjust the positional relationship.

47. A scanning exposure apparatus according to claim 36, wherein said variable field diaphragm has four blades to define a width of an illumination region in a scanning direction of the mask and in a direction perpendicular to the scanning direction.

48. A scanning exposure apparatus according to claim 47, wherein said sensor has measurement points outside of the exposure region.

49. A scanning exposure apparatus according to claim 47, wherein said sensor had measurement points inside of the exposure region.

50. An scanning exposure apparatus according to claim 47, wherein said sensor has measurement points inside and outside of the exposure region.

51. A scanning exposure apparatus according to claim 47, wherein said measurement points are included in one of two groups of measurement points respectively arranged in opposite sides of said exposure region with respect to a direction parallel to the movement direction of the substrate.

52. A scanning exposure apparatus according to claim 51, wherein said one group of measurement points is chosen according to the scanning direction of the substrate.