Projection exposure apparatus having an off-axis alignment system and method of alignment therefor

• US 5,243,195 A
• Filed: 12/29/1992
• Issued: 09/07/1993
• Est. Priority Date: 04/25/1991
• Status: Expired

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Nishi, Kenji
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): SHAMI, KHALED
• Application Number:
  US07/998,642
• Time in Patent Office: 252 Days
• Field of Search: 250/548, 250/557, 250/237 G, 250/237 R, 356/399, 356/400, 356/401
• US Class Current: 250/548
• CPC Class Codes: G03F 7/70691 Handling of masks or workpieces
• CPC Class Codes: G03F 9/7088 Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection

Abstract

An exposure apparatus for exposing mask patterns on a sensitive plate comprises a set (for X and Y direction) of a laser interferometer for measuring a position of a wafer stage and satisfying Abbe'"'"'s condition with respect to a projection lens and a set (for X and Y direction) of the laser interferometer and satisfying Abbe'"'"'s condition with respect to off-axis alignment system.

When a fiducial mark on the wafer stage is positioned directly under the projection lens, a presetting is performed so that measuring values by the two sets of laser interferometers are equal to each other.

Claims

1. An exposure apparatus for exposing mask patterns on a sensitive plate having,

a mask stage holding said mask,

a plate stage movable two dimensionally in accordance with a rectangular coordinate system while holding said sensitive plate,

a projection optical system imaging said mask patterns at a predetermined position on said sensitive plate,

a first mark detecting system for detecting a mask mark formed at a predetermined position on said mask in the image field of said projection optical system, and

a second mark detecting system for detecting a plate mark formed on said sensitive plate in a detection area positioned at predetermined intervals from the optical axis of said projection optical system,

said exposure apparatus comprising:

(a) a first fiducial mark member arranged on a part of said plate stage, having a shape capable of being detected by said first mark detecting system through said projection optical system;

(b) a second fiducial mark member arranged on a part of said plate stage, having a shape capable of being detected by said second mark detecting system; and

(c) a mounting member for mounting said first fiducial mark member and said second fiducial mark member at constant intervals recognized in advance so as to position said second fiducial mark member in the detection area of said second mark detecting system when said first fiducial mark member is positioned in a predetermined relationship with respect to the position where said mask mark is to be present in the image field of said projection optical system.

2. An exposure apparatus for exposing mask patterns on a sensitive plate having,

a mask stage holding said mask,

a plate stage movable two dimensionally in accordance with a rectangular coordinate system while holding said sensitive plate,

a projection optical system imaging said mask patterns at a predetermined position on said sensitive plate,

a first mark detecting system for detecting a mask mark formed at a predetermined position on said mask in the image field of said projection optical system, and

a second mark detecting system having a detection center positioned at predetermined intervals apart from the optical axis of said projection optical system, for detecting a plate mark formed on said sensitive plate,

said exposure apparatus comprising:

(a) a first fiducial mark member arranged on a part of said plate stage and capable of being detected by said first mark detecting system through said projection optical system;

(b) a second fiducial mark member arranged on a part of said plate stage, and capable of being detected by said second mark detecting system;

(c) a mounting member for mounting said first fiducial mark member and said second fiducial mark member at constant intervals recognized in advance so as to position said second fiducial mark member in the detection area of said second mark detecting system when said first fiducial mark member is positioned in a predetermined relationship with respect to the position where said mask mark is to be present in the image field of said projection optical system; and

(d) base line determining means for calculating the base line distance between the projecting position of said mask patterns by said projection optical system and the position of the detection center of said second mark detecting system based on the positional displacement value between said first fiducial mark member and said mask mark detected by said first mark detecting system, the positional displacement value of said second fiducial mark member against said detection center detected by said second mark detecting system, and the value of said constant intervals recognized in advance.

3. An exposure apparatus for exposing mask patterns on a sensitive plate having a plate stage movable two dimensionally in accordance with a rectangular coordinate system while holding said sensitive plate, a projection optical system imaging said mask patterns at a predetermined position on said sensitive plate, a first mark detecting system for detecting a mask mark formed at a predetermined position on said mask in the image field of said projection optical system, and a second mark detecting system, having a detection area positioned at predetermined intervals apart from the optical axis of said projection optical system, for detecting a plate mark formed on said sensitive plate, said exposure apparatus comprising:

(a) a first fiducial mark member arranged on a part of said plate stage and capable of being detected by said first mark detecting system through said projection optical system;

(b) a second fiducial mark member arranged on a part of said plate stage, and capable of being detected by said second mark detecting system;

(c) a mounting member for mounting said first fiducial mark member and said second fiducial mark member at constant intervals recognized in advance so as to position said second fiducial mark member in the detection area of said second mark detecting system when said first fiducial mark member is positioned in a predetermined relationship with respect to the position where said mask mark is to be present in the image field of said projection optical system;

(d) positioning control means for causing said plate stage to be stationary on said rectangular coordinate system so as to enable said mask mark and said first fiducial mark member to be detected in an aligned state by said first mark detecting system;

(e) means for starting the detecting operation of said second mark detecting system for said second fiducial mark member while said positioning control means is activating; and

(f) base line determining means for calculating the base line distance between the projecting position of said mask patterns by said projection optical system and the position of the detection area of said second mark detecting system based on the positional displacement value of said second fiducial mark member detected by said second mark detecting system, and the value of said constant intervals recognized in advance.

4. An exposure apparatus for exposing mask patterns on a sensitive plate having a plate stage movable two dimensionally in accordance with a rectangular coordinate system while holding said sensitive plate, a projection optical system imaging said mask patterns at a predetermined position on said sensitive plate, a first mark detecting system for detecting a mask mark formed at a predetermined position on said mask in the image field of said projection optical system, and a second mark detecting system, having a detection area positioned at predetermined intervals apart from the optical axis of said projection optical system, for detecting a plate mark formed on said sensitive plate, said exposure apparatus comprising:

(a) a first fiducial mark member arranged on a part of said plate stage and capable of being detected by said first mark detecting system through said projection optical system;

(b) a second fiducial mark member arranged on a part of said plate stage, and capable of being detected by said second mark detecting system;

(c) a mounting member for mounting said first fiducial mark member and said second fiducial mark member at constant intervals recognized in advance so as to position said second fiducial mark member in the detection area of said second mark detecting system when said first fiducial mark member is positioned in a predetermined relationship with respect to the position where said mask mark is to be present in the image field of said projection optical system;

(d) positioning control means for causing said plate stage to be stationary on said rectangular coordinate system so as to enable said detection area and said first fiducial mark member to be detected in an aligned state by said second mark detecting system;

(e) means for starting the detecting operation of said mask mark and said second fiducial mark member by said first mark detecting system while said positioning control means is activating; and

(f) base line determining means for calculating the base line distance between the projecting position of said mask patterns by said projection optical system and the position of the detection area of said second mark detecting system based on the positional displacement value between said mask mark and said second fiducial mark member detected by said first mark detecting system, and the value of said constant intervals recognized in advance.

5. An exposure apparatus for exposing mask patterns on a sensitive plate including a projection optical system imaging said mask patterns at a predetermined image plane position on said sensitive plate, a plate stage movable two dimensionally in accordance with a rectangular coordinate system parallel to said image plane while holding said sensitive plate, a first mark detecting system for detecting a mark on said sensitive plate through a first detecting area provided in the projection image field of said projection optical system, a second mark detecting system for detecting a mark on said sensitive plate through a second detecting area provided outside the projection image field of said projection optical system, said exposure apparatus comprising:

(a) a fiducial member mounted on a part of said plate stage with a first fiducial mark capable of being detected by said first mark detecting system and a second fiducial mark capable of being detected by said second mark detecting system, said first and second fiducial marks being formed at predetermined constant intervals, wherein said first and second fiducial marks are provided in a positional relationship substantially the same as the arrangement of said first and second detecting areas in said rectangular coordinate system;

(b) a first measuring means of an incremental type having measuring axes arranged in parallel with each of the two coordinate axes of said rectangular coordinate system to satisfy the Abbe'"'"'s condition with respect to the optical axis of said projection optical system for measuring the coordinate positions on said rectangular coordinate system of said plate stage;

(c) a second measuring means of an incremental type having measuring axes arranged in parallel with each of the two coordinate axes of said rectangular coordinate system to satisfy the Abbe'"'"'s condition with respect to the second detecting area of said second mark detecting system for measuring the coordinate positions on said rectangular coordinate system of said plate stage; and

(d) resetting means for resetting each of the measured values of said first and second measuring means to a same value when said plate stage is positioned so that said first fiducial mark is detected by said first mark detecting system and at the same time, said second fiducial mark is detected by said second mark detecting system.

6. An exposure apparatus for exposing mask patterns on a sensitive plate including a projection optical system imaging said mask patterns at a predetermined image plane position of said sensitive plate, a plate stage movable two dimensionally in accordance with a rectangular coordinate system parallel to said image plane while holding said sensitive plate, a first mark detecting system for detecting a mask mark on said mask through a detecting area provided in the projection image field of said projection optical system, a second mark detecting system for detecting a mark on said sensitive plate through a detecting area provided outside the projection image field of said projection optical system, said exposure apparatus comprising:

(a) a fiducial member provided on a part of said plate stage and having a fiducial mark detecting by said first mark detecting system;

(b) positioning control means for driving said plate state and for causing said plate stage to be stationary in order to arrange said fiducial mark at a predetermined position in the image field of said projection optical system for enabling said first mark detecting system to detect both said mask mark and said fiducial mark;

(c) a first measuring means of an incremental type having measuring axes arranged in parallel with each of the two coordinate axes of said rectangular coordinate system to satisfy the Abbe'"'"'s condition with respect to the optical axis of said projection optical system for measuring the coordinate positions on said rectangular coordinate system of said plate stage;

(d) a second measuring means of an incremental type having measuring axes arranged in parallel with each of the two coordinate axes of said rectangular coordinate system to satisfy the Abbe'"'"'s condition with respect to the detection area of said second mark detecting system for measuring the coordinate positions on said rectangular coordinate system of said plate stage; and

(e) resetting means for resetting each of the measured values of said first and second measuring means to a same value when said plate stage is positioned by said positioning control means.

7. An exposure apparatus for exposing mask patterns on a sensitive plate including a mask stage movable two dimensionally while holding said mask, a projection optical system for imaging said mask patterns on said sensitive plate, a plate stage movable two dimensionally in a rectangular coordinate system while holding said sensitive plate, and a first mark detecting system for detecting mask marks formed at a plurality of positions on said mask in the projection image field of said projection optical system, said exposure apparatus comprising:

(a) a fiducial member provided on a part of said plate stage with a first fiducial marks being formed to be aligned with each of said mask marks through the projection image field of said projection optical system;

(b) means for storing values of mounting errors of said fiducial member on said plate stage in advance with said rectangular coordinate system as reference;

(c) a first control means for driving said plate stage and for causing said plate stage to be stationary so as to arrange said plurality of fiducial marks at predetermined positions in the projection image field of said projection optical system; and

(d) a second control means for positioning said mask stage on the basis of the detection of said first mark detecting system so that said mask marks are displaced by said mounting errors to be aligned with respect to said plurality of fiducial marks at said predetermined positions.

8. An exposure apparatus for exposing mask patterns on a sensitive plate having a mark stage holding said mask, a plate stage movable two dimensionally in accordance with a rectangular coordinate system while holding said sensitive plate, a projection optical system for imaging said mask patterns on said sensitive plate, an inner-field alignment system for detecting the patterns formed on an object on said plate stage through the image field of said projection optical system, and an outer-field alignment system for detecting the patterns of said object, said exposure apparatus comprising:

(a) a fiducial member of a low expansion material mounted on a part of said plate stage with a first fiducial mark capable of being detected by said inner-field alignment system and a second fiducial mark capable of being detected by said outer-field alignment system being formed on the surface thereof, wherein said first and second fiducial marks are provided in a positional relationship substantially the same as the arrangement the mark detecting areas of said inner-field alignment system and said outer-field alignment system in said rectangular coordinate system;

(b) positioning control means of positioning said plate stage to cause said first fiducial mark to be stationary at a predetermined position in the image field of said projection optical system; and

(c) means for instructing said inner-field alignment system and said outer-field alignment system to detect respectively said first fiducial mark and said second fiducial mark almost simultaneously with said plate stage being at rest.

9. A method for controlling the precision of an exposure apparatus for exposing mask patterns on a sensitive plate provided with a mask stage holding said mask, a plate stage movable two dimensionally in accordance with a rectangular coordinate system while holding said sensitive plate, an alignment system for detecting at least one of a mask mark formed on said mask and a plate mark formed on said sensitive plate for the alignment of said mask and said sensitive plate, and a fiducial member arranged on a part of said plate stage with a fiducial mark formed thereon to be detected by said alignment system, including the following steps of:

(a) aligning said mask with respect to said fiducial member by arranging the fiducial mark of said fiducial member at an exposing position in said rectangular coordinate system and detecting said mask mark and fiducial mark using said alignment system;

(b) sequentially exposing said mask patterns on said sensitive plate for each of step positions by moving said plate stage in the direction of one of the coordinate axes of said rectangular coordinate system step by step for a predetermined amount, wherein said mask patterns are partially overlapped in the direction of the step movement for exposure;

(c) measuring a positional deviating amount of said overlapped portions of the patterns exposed on said sensitive plate in a direction intersecting at right angles with said direction of the step movement; and

(d) calculating the mounting error of said fiducial member on said plate stage with said rectangular coordinate system as reference on the basis of said measured positional deviating amount.

10. An exposure apparatus for exposing mask patterns on a sensitive plate including:

a plate stage movable two dimensionally in accordance with a rectangular coordinate system while holding said sensitive plate,

a projection optical system for imaging said mask patterns on said sensitive plate,

a light emission mark member mounted on a part of said plate stage for forming a fine light emission mark image on said mask through said projection optical system,

a first detecting system for detecting variation of the light being generated when said light emission mark image scans a mark formed on said mask, and

a second detecting system for detecting a mark on said sensitive plate by scanning said plate stage through a detecting area arranged outside the image field of said projection optical system, comprising the following;

(a) a fiducial member mounted on a part of said plate stage at a predetermined interval with respect to said light emission mark member with a fiducial mark formed thereon to be detected by said second detecting system, where the light emission mark of said light emission mark member and the fiducial mark of said fiducial member are provided in a positional relationship substantially the same as the arrangement of the expected position of the projection of the mark of said mask by said projection of the mark of said mask by said projection optical system and the position of the detecting area of said second detecting system in said rectangular coordinate system;

(b) driving control means for scanning said plate stage in a predetermined direction so as to cause said fiducial mark to pass through the detecting area of said second detecting system while said light emission image by said projection optical system scans only a predetermined area including said mask mark; and

(c) means for storing signals output from each of the first detecting system and said second detecting system while said plate stage is scanned.

11. An exposure apparatus for exposing mask patterns on a sensitive plate including:

a plate stage movable two dimensionally in accordance with a rectangular coordinate system while holding said sensitive plate, p1 a projection optical system for imaging said mask patterns on said sensitive plate,

a first detecting system mounted on a part of said plate stage for detecting photoelectrically mark imaging light from said mask projected by said projection optical system through a light receiving area, and

a second detecting system for detecting a mark on said sensitive plate photoelectrically through a detecting area arranged outside the image field of said projection optical system, comprising the following;

(a) a fiducial member mounted on a part of said plate stage at predetermined interval with respect to said first detecting system with a fiducial mask formed thereon to be detected by said second detecting system, wherein the light receiving area of said first detecting system and the fiducial mark of said fiducial member are provided in a positional relationship substantially the same as the arrangement of the expected position of the image mark imaging light from said mask by said projection optical system and the position of the detection area of said second detecting system in said rectangular coordinate system; and

(b) driving control means for driving said plate stage to cause said fiducial mark to be detected by said second detecting system substantially at the same time that the mark imaging light from said mask by said projection optical system is detected by said first detecting system.