Method and apparatus for exposure process

• US 5,298,761 A
• Filed: 06/16/1992
• Issued: 03/29/1994
• Est. Priority Date: 06/17/1991
• Status: Expired due to Term

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Aoki, Atsuyuki, Yokota, Muneyasu
• Primary Examiner(s): MESSINGER, MICHAEL
• Application Number:
  US07/899,549
• Time in Patent Office: 651 Days
• Field of Search: 250/548, 250/557, 356/401, 356/399-400
• US Class Current: 250/548
• CPC Class Codes: G02F 1/13625 Patterning using multi-mask exposure
• CPC Class Codes: G03F 7/70475 Stitching, i.e. connecting image fields to produce a device field, the field occupied by a device such as a memory chip, processor chip, CCD, flat panel display
• CPC Class Codes: G03F 7/708 Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
• CPC Class Codes: G03F 9/70 for microlithography measuring printed patterns for monitoring overlay G03F7/70633 or focus G03F7/70641; projection system adjustment G03F7/70258; position control G03F7/70775

Abstract

In the manufacture of a device having a relatively large area, e.g., a liquid crystal device by a lithographic technique, using at least one of a plurality of original images and defining an exposed pattern by each original image as an individual subdivision area, the position of a substrate is changed relatively upon exposure of every subdivision area to expose on the substrate a composite exposed pattern of a relatively large area composed of the plurality of abutting and combined subdivision areas. When aligning each of the original images with the substrate in accordance with predetermined target position information, the amounts of relative deviation at the abutting portions of the subdivision areas (i.e., stitching errors) are preliminarily determined and compensating values tending to reduce each of the stitching errors to less than a given tolerance value are added to the target position information, thereby effecting the alignment. Thus, the stitching accuracy is improved for the composite pattern on the whole.

Claims

1. A method of using at least one of a plurality of original images each containing the same or a different pattern, and moving positions of a light-sensitive substrate and each of said original images relatively so as to successively expose said patterns in such a manner that a plurality of subdivision areas, each composed of an exposure area of each of said original images, are abutted and combined thereby exposing a composite pattern composed of said plurality of patterns stitched together on said light-sensitive substrate, whereby when aligning said original images and said light-sensitive substrate pattern by pattern in accordance with predetermined target position information, said method comprising the steps of:

preliminarily determining amounts of relative deviation in exposure position at abutting portions of said subdivision areas in said composite pattern;

adding compensating values to said target position information so as to reduce said amounts of deviation in exposure position at said abutting portions to less than a predetermined tolerance value; and

aligning said original images and said light-sensitive substrate pattern by pattern.

2. A method according to claim 1, wherein said compensating values are computed by statistically calculating said amounts of deviation in exposure position in such a manner that said amounts of deviation in exposure position at said abutting portions are reduced on an average.

3. A method according to claim 1, wherein positions of at least two mark patterns preliminarily provided for each of said original images are measured as positional coordinates for a reference position of an exposure apparatus, and wherein said amounts of deviation in exposure position are determined in accordance with results of measurement of said original images associated so as to form said abutting subdivision areas.

4. A method according to claim 1, wherein a test exposure is preliminarily performed for at least pair of said original images which form abutting subdivision areas, and wherein said amounts of deviation in exposure position are obtained by actual measurement from results of said trial exposure.

5. A method according to claim 4, wherein when effecting said test exposure, an effective exposure area is widened thereby effecting a test exposure including mark patterns formed on a peripheral portion of each of said original images.

6. A method according to claim 4, wherein each of said original images is preliminarily formed with a plurality of mark patterns each including vernier scales respectively constituting a micrometer-like main gauge and an auxiliary gauge and arranged at locations corresponding to said abutting portions associated therewith whereby at the time of said test exposure, the scales of said mark patterns exposed on said light-sensitive substrate are read to determine said amounts of relative deviation in exposure position at said abutting portions.

7. A method according to claim 4, wherein after said test exposure has been effected, the resulting exposed patterns are developed whereby positions of the mark patterns of said subdivision areas are measured as positional coordinates with respect to said apparatus reference position, and in accordance with results of said measurement of said abutting subdivision areas said amounts of relative deviation in exposure position are determined.

8. A method according to claim 7, wherein said test exposure, said development and said position measurement of said developed mark patterns are successively performed by a system of units including substrate conveying means.

9. A method according to claim 1, wherein said amounts of deviation in exposure position are determined on the basis of one of said original images exposed first whereby the other of said original images to be exposed second and subsequently are each caused to make linear movements and/or a rotational movement relative to said light-sensitive substrate by amounts of compensating values corresponding to said amounts of deviation in exposure position of said first original image thereby aligning the same with said light-sensitive substrate.

10. A method according to claim 1, wherein said light-sensitive substrate comprises a glass substrate whose surface is covered with a thin light-sensitive film.

11. A method of using at least one of a plurality of original images each containing the same or a different pattern, and moving a light-sensitive substrate in stepping movements of a predetermined amount so as to abut and combine at least three subdivisional areas each composed of an exposure area of one of said original images thereby successively exposing said patterns to expose a composite pattern including at least three of said patterns stitched together on said light-sensitive substrate, whereby when aligning said original images and said light-sensitive substrate pattern by pattern in accordance with predetermined target position information, said method comprising the steps of:

preliminarily determining amounts of deviation in exposure position at an abutting poriton of at least two of said subdivision areas in said composite pattern;

adding compensating values to said predetermined target position information in such a manner that said amounts of deviation in exposure position at said abutting portion of said at least two original images are reduced to less than a predetermined tolerance value; and

aligning said original images and said light-sensitive substrate pattern by pattern.

12. An exposure apparatus comprising:

stage means adapted to hold a light-sensitive substrate and movable within a plane;

holding means for holding a plurality of original images each containing an optical pattern to be transferred on said light-sensitive substrate substantially parallel to said light-sensitive substrate;

original image alignment means for aligning each of said original images with respect to a reference position of said exposure apparatus;

optical means for exposing the pattern of each of said original images on said light-sensitive substarate;

moving means for moving said light-sensitive substrate on said stage means relative to each of said original images;

control means whereby when successively exposing on the same light-sensitive substrate at least one of said plurality of original images each containing the same or a different pattern, said moving means is controlled in accordance with predetermined position information in such manner that a plurality of subdivision areas each composed of an exposure area by at least one of said original images are abutted and combined; and

compensating means for calculating compensating values tending to reduce predetermined amounts of relative deviation in exposure position at the abutting portions of said subdivision areas to less than a predetermined tolerance value and applying said compensating values to said control means and said original image alignment means.

13. An apparatus according to claim 12, further comprising measuring means for measuring positions of at least two mark patterns preliminarily provided for each of said original images as positional coordinates with respect to the reference position of said exposure apparatus, and wherein said compensating means calculates said compensating values in accordance with results of said measurement of said original images which are to form abutting subdivision areas.

14. An apparatus according to claim 13, wherein said measuring means includes reference marks fixedly mounted on said stage means, and projection means for inversely projecting said reference marks on each of said original images whereby said stage means is moved so as to scan the mark patterns of each of said original images by the inverse projected images of said reference marks, thereby measuring the positions of said mark patterns on said exposure apparatus.

15. An apparatus according to claim 12, further comprising means for detecting the mark patterns of each of said original images exposed and developed on said light-sensitive substrate, said detecting means including means for projecting a slit-like light beam onto each of said mark patterns, and light sensing means for receiving diffracted beams from said developed patterns whereby said stage means is moved to scan said mark patterns by said light beam and thereby to detect said mark patterns.

16. An apparatus according to claim 12, wherein said original image alignment means comprises a plurality of alignment microscopes for aligning each of said original images with said apparatus reference position, and wherein said compensating means adds said compensating values to collimation positions of said alignment microscopes.

17. An apparatus according to claim 12, wherein, said optical means includes a variable field aperture for varying said effective exposure area.

18. An apparatus according to claim 12, wherein said light-sensitive substrate comprises a glass substrate whose surface is covered with a thin light-sensitive film.