Exposure method and apparatus

• US 5,448,332 A
• Filed: 11/21/1994
• Issued: 09/05/1995
• Est. Priority Date: 12/25/1992
• Status: Expired due to Term

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Nishi, Kenji, Tanaka, Yasuaki, Sakakibara, Yasuyuki, Murakami, Seiro
• Primary Examiner(s): WINTERCORN, RICHARD
• Application Number:
  US08/345,325
• Time in Patent Office: 288 Days
• Field of Search: 355/43, 355/53, 355/55, 250/548, 250/561, 250/563, 250/442.1, 356/400, 356/401
• US Class Current: 355/53
• CPC Class Codes: G03F 7/70358 Scanning exposure, i.e. relative movement of patterned beam and workpiece during imaging
• CPC Class Codes: G03F 9/7026 Focusing

Abstract

An apparatus for exposing a pattern, formed on a mask, on each of a plurality of partitioned areas on a photosensitive substrate by a step-and-repeat scheme includes a projection optical system for projecting the pattern of the mask on the photosensitive substrate, a substrate stage for holding the photosensitive substrate and two-dimensionally moving the photosensitive substrate within a plane perpendicular to the optical axis of the projection optical system, a detection unit for projecting a pattern image having a predetermined shape on the photosensitive substrate and photoelectrically detecting light reflected by the photosensitive substrate to detect a position at each of a plurality of points on the photosensitive substrate along the optical axis of the projection optical system, and a measurement unit for, when each of a plurality of measurement points in a partitioned area on which a pattern of the mask is to be exposed next coincides with or approaches the pattern image, detecting an offset amount between an imaging plane of the projection optical system and the next partitioned area along the optical axis during a stepping operation of the substrate stage, wherein the imaging plane and the next partitioned area are relatively moved along the optical axis in accordance with the measured offset amount before the pattern of the mask is exposed on the next partitioned area.

Claims

1. An apparatus for exposing a pattern, formed on a mask, on each of a plurality of partitioned areas on a photosensitive substrate by a step-and-repeat scheme, comprising:

a projection optical system for projecting the pattern of the mask on the photosensitive substrate;

a substrate stage for holding the photosensitive substrate and two-dimensionally moving the photosensitive substrate within a plane perpendicular to an optical axis of said projection optical system;

means for projecting a pattern image having a predetermined shape on the photosensitive substrate and photoelectrically detecting light reflected by the photosensitive substrate to detect a position at each of a plurality of points on the photosensitive substrate along an optical axis of said projection optical system; and

means for, when each of a plurality of measurement points in a partitioned area on which a pattern of the mask is to be exposed next coincides with or approaches the pattern image, detecting an offset amount between an imaging plane of said projection optical system and the next partitioned area along the optical axis during a stepping operation of said substrate stage,

wherein the imaging plane and the next partitioned area are relatively moved along the optical axis in accordance with the measured offset amount before the pattern of the mask is exposed on the next partitioned area.

2. An apparatus according to claim 1, wherein

said measurement means-includes calculation means for performing a statistical calculation of the plurality of positions to calculate a plane position of the next partitioned area, and obtains an offset amount along the optical axis and a relative inclination amount of the imaging plane and the next partitioned area on the basis of the calculated plane position, and

said apparatus further comprises correction means for relatively inclining the imaging plane and the next partitioned area and also relatively moving the imaging plane and the next partitioned area along the optical axis so as to reduce the inclination amount and the offset amount to zero.

3. An apparatus according to claim 2, wherein said correction means includes a movable table on which the photosensitive substrate is placed and which can be inclined with respect to an imaging plane of said projection optical system and can be finely moved along the optical axis.

4. An apparatus according to claim 1, wherein said detection means includes means for projecting a pattern image at each of a plurality of positions in a projection field of view of said projection optical system, and means for selecting some of the plurality of pattern images in accordance with a stepping direction of said substrate stage, so that a position at each of a plurality of measurement points in the next partitioned area along the optical axis is detected by using the selected pattern images.

5. An apparatus for scanning/exposing a pattern of a mask on a photosensitive substrate, comprising:

a mask stage capable of holding the mask and moving in a predetermined direction along a plane of the pattern;

a projection optical system for projecting the pattern of the mask on the photosensitive substrate;

a substrate stage capable of holding the photosensitive substrate and moving in the predetermined direction;

means for synchronously driving said mask stage and said substrate stage when the pattern of the mask is to be scanned/exposed on a partitioned area on the photosensitive substrate;

means for projecting a plurality of pattern images on the photosensitive substrate and photoelectrically detecting light reflected by the photosensitive substrate to detect a position at each of a plurality of points on the photosensitive substrate along an optical axis of said projection optical system, said means including means for projecting at least one of the pattern images on each of two sides of a projection area, on which the pattern of the mask is to be projected by said projection optical system, in the predetermined direction; and

means for causing an imaging plane of said projection optical system and the partitioned area to coincide with each other along the optical axis during the scan/exposure on the basis of position information output from said detection means.

6. An apparatus for scanning/exposing a pattern of a mask on a photosensitive substrate, comprising:

a projection optical system for projecting the pattern of the mask on the photosensitive substrate;

a multi-point measurement system for detecting a position at each of a plurality of points on the photosensitive substrate along an optical axis of said projection optical system;

calculation means for calculating an inclination angle between the photosensitive substrate and an imaging plane of said projection optical system on the basis of a detection result obtained by said multi-point measurement system;

a table capable of holding the photosensitive substrate and being inclined relative to the imaging plane of said projection optical system; and

means for setting a response speed of said table which is inclined in accordance with the calculated inclination angle, said means setting a response speed of said table with respect to a scan direction of the photosensitive substrate to be different from a response speed of said table with respect to a direction perpendicular to the scan direction.

7. An apparatus for scanning/exposing a pattern of a mask on a photosensitive substrate, comprising:

a projection optical system for projecting the pattern of the mask on the photosensitive substrate;

means for relatively moving the photosensitive substrate and an imaging plane of said projection optical system along an optical axis;

means for detecting a deviation between the photosensitive substrate and the imaging plane of said projection optical system at each of a plurality of measurement points separated from a projection area, on which the pattern of the mask is to be projected by said projection optical system, by a predetermined distance; and

means for controlling said relative moving means on the basis of maximum and minimum values of the plurality of detected deviations.

8. A scanning exposure apparatus comprising:

a projection optical system for projecting a pattern of a mask on a photosensitive substrate;

a scanning system for respectively scanning said mask and said substrate along a predetermined direction substantially perpendicular to an optical axis of said projection optical system, in order to transcribe an image of the pattern onto a partitioned area on said substrate;

a measuring system having at least one measuring point remote from a projection area of said projection optical system where the pattern image is formed, along the predetermined direction, said measuring system detecting positional information of said substrate at the measuring point in a direction along the optical axis; and

a driving device for relatively moving said substrate and the image plane of said projection optical system during the scan thereof in accordance with the detected positional information, so that the image plane of said projection optical system is coincident with the partitioned area within the projection area.

9. An apparatus according to claim 8, wherein said projection optical system has a circular image field, and said apparatus further comprises an illumination system for illuminating said mask, said illumination system having a field stop for defining the projection area as a rectangular projection area within the circular image field.

10. An apparatus according to claim 9, wherein the rectangular projection area extends from the optical axis which is a center thereof, substantially along a diameter direction of said circular image field perpendicular to the scanning direction of said substrate.

11. An apparatus according to claim 8, wherein said scanning system includes a mask stage which carries said mask and is movable along said predetermined direction, a substrate stage which carries said substrate and is movable along the predetermined direction, and a member for driving said mask stage and said substrate stage so as to synchronously scan said mask and said substrate at a speed ratio based upon a projection magnification of said projection optical system.

12. An apparatus according to claim 8, wherein said driving device includes a movable member which is movable along the optical axis direction while carrying said substrate and is capable of inclining with respect to an image plane of said projection optical system, and includes a member for driving said movable member in accordance with the detected positional information.

13. An apparatus according to claim 8, wherein said measuring system includes an optical device for irradiating a light beam to the at least one measuring point and for receiving a light beam reflected at said substrate.

14. An apparatus according to claim 8, further comprising a stage for moving said substrate in a plane perpendicular to the optical axis so as to expose the image of the pattern to each part of said partitioned area on said substrate in a step-and-scan manner.

15. An apparatus according to claim 8, further comprising a device for detecting a deviation along the optical axis direction and a relative inclination between the image plane of said projection optical system and said partitioned area based on the detected positional information,

wherein said driving device relatively moves and relatively inclines the image plane of said projection optical system and said substrate based on the detected deviation and relative inclination.

16. An apparatus according to claim 8, wherein said measuring system has at least one measuring point at each of opposite sides of the projection area, and includes an optical device for irradiating a light beam to the each of the measuring points and for receiving a light beam reflected at said substrate.

17. An apparatus according to claim 16, wherein said measuring system has a plurality of measuring points at each of opposite sides of the projection area, said plurality of measuring points being arranged substantially along a direction perpendicular to a scan direction of said substrate.

18. An apparatus according to claim 16, further comprising a controller for selecting one of said plurality of measuring points in accordance with the scan direction of the substrate.

19. An apparatus according to claim 18, wherein said driving device includes a movable member which is movable along the optical axis direction while carrying said substrate, and is capable of inclining with respect to an image plane of said projection optical system, and includes a member for driving said movable member in accordance with the positional information obtained at the selected measuring point, detected by said measuring system.

20. An apparatus according to claim 8, wherein said measuring system has a plurality of measuring points at an outer side of the projection area, which are remote therefrom by a predetermined distance along a direction perpendicular to a scan direction of said substrate, and includes an optical device for irradiating a light beam to each of the measuring points and for receiving a light beam reflected at said substrate.

21. An apparatus according to claim 20, wherein said plurality of measuring points are arranged substantially along a direction perpendicular to the scan direction of said substrate.

22. An apparatus according to claim 20, further comprising a device for detecting a relative inclination amount between the image plane of said projection optical system and said partitioned area based on the detected positional information obtained at each of said plurality of measuring points,

wherein said driving device relatively inclines the image plane of said projection optical system and said substrate based on the detected inclination amount.

23. An apparatus according to claim 22, wherein said driving device includes a table capable of inclining with respect to the image plane of said projection optical system while carrying said substrate, a member for driving said table, and an adjusting device for varying a servo-gain of said driving member to adjust a response speed of said table, said adjusting device adjusting the response speed in accordance with a variation of a scan speed of said substrate.

24. An apparatus according to claim 22, wherein said detecting device detects a relative inclination amount of the image plane of said projection optical system and said partitioned area along the scan direction of said substrate, based on the information relating to a plurality of positions sequentially detected at each measuring point by said measuring system in accordance with the scan of said substrate, wherein said driving device relatively inclines the image plane of said projection optical system and said substrate, in accordance with two detected inclination amounts.

25. An apparatus according to claim 24, wherein said driving device includes a table capable of inclining with respect to the image plane of said projection optical system while carrying said substrate, and a member for driving said table in accordance with said two detected inclination amounts.

26. An apparatus according to claim 25, wherein said driving device includes a device for setting a response speed of said table, said setting device making the response speed of said table along the scan direction of said substrate different from a response speed of said table along a direction perpendicular to the scan direction.

27. An apparatus according to claim 25, wherein said driving device includes a device for adjusting a response speed of said table, said adjusting device adjusting the response speed in accordance with a variation of a scan speed of said substrate.

28. An apparatus according to claim 25, wherein said detecting device detects a deviation along the optical axis between the image plane of said projection optical system and said partitioned area based on the information relating to the plurality of positions, and said driving device relatively moves and relatively inclines the image plane of said projection optical system and said substrate based on the detected inclination amount and the detected deviation.

29. An apparatus according to claim 22, further comprising a device for detecting a deviation along the optical axis between the image plane of said projection optical system and said partitioned area based on the information obtained at each of the plurality of measuring points,

wherein said driving device relatively moves the image plane of said projection optical system and said substrate along the optical axis direction, based on the detected inclination amount and the detected deviation.

30. An apparatus according to claim 8, wherein said measuring system has at least one first measuring point set within the projection area and at least one second measuring point set at an outer side of the projection area, and includes an optical device for irradiating a light beam to each of the first and the second measuring points and for receiving a light beam reflected at said substrate.

31. An apparatus according to claim 30, wherein said measuring system has a plurality of the first and the second measuring points, the first and the second measuring points being respectively arranged substantially along a direction perpendicular to a scan direction of said substrate.

32. An apparatus according to claim 30, further comprising a device for detecting a deviation along the optical axis direction and a relative inclination amount between the image plane of said projection optical system and said partitioned area, based on the positional information at each of the first and the second measuring points, detected by said measuring system,

wherein said driving device relatively moves along the optical axis direction and inclines the image plane of said projection optical system and said substrate based on the detected deviation and the detected inclination amount.

33. An apparatus according to claim 30, further comprising a device for detecting a deviation along the optical axis direction and a relative inclination amount between the image plane of said projection optical system and said partitioned area, based on the positional information at each of the first and the second measuring points, detected by said measuring system,

wherein said driving device includes a movable member which is movable along the optical axis direction while carrying said substrate, is capable of inclining with respect to the image plane of said projection optical system, and includes a member for driving said movable member in accordance with the detected deviation, the detected inclination amount and the information at the first measuring point, detected by said measuring system.

34. An apparatus according to claim 30, further comprising a device for detecting a deviation along the optical axis direction and a relative inclination amount between the image plane of said projection optical system and said partitioned area, based on the detected positional information, said device having a first mode in which the positional information obtained at a second measuring point is used, and a second mode in which the positional information obtained at each of the first and the second measuring points is used,

wherein said driving device relatively moves along the optical axis direction and inclines the image plane of said projection optical system and said substrate based on the deviation and the inclination amount detected through either one of the first mode and the second mode.

35. An apparatus according to claim 8, wherein said measuring system has at least one first measuring point set within the projection area, at least one second measuring point set at an outer side of the projection area, and at least one third measuring point opposing the second measuring point through the projection area, and includes an optical device for irradiating a light beam to each of the first, the second and the third measuring points and for receiving a light beam reflected at said substrate.

36. An apparatus according to claim 35, wherein said measuring system has a plurality of the first, the second and the third measuring points, the first, the second and the third measuring points being respectively arranged substantially along a direction perpendicular to a scan direction of said substrate.

37. An apparatus according to claim 35, further comprising a controller for selecting one of the first, the second and the third measuring points, in accordance with a scan direction of said substrate,

wherein said driving device relatively moves along the optical axis direction and inclines the image plane of said projection optical system and said substrate based on the positional information obtained at each of the selected measuring points.

38. An apparatus according to claim 8, wherein said measuring system includes a multi-point optical device for irradiating a light beam to each measuring point and for receiving a light beam reflected at said substrate, said apparatus further comprising a controller for selecting at least one measuring point in accordance with a relative position between the partitioned area and the projection area, said controller changing at least one of a number and a position of the selected measuring point, in response to a variation of the relative position due to the scan of said substrate.