US4904087A
Expired / Lapsed
US
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Method for aligning photomasks
Assignee: AMERICAN TELEPHONE and TELEGRAPH Co AT&T BELL LABORATORIES
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Filing: 1988-11-21
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Granted: 1990-02-27
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Expires: 2008-11-21
Abstract
Abstract Photomasks (11, 12) are aligned on opposite sides of a wafer by directing light beams through zone plates (13 A-C) in one photomask and through aligned transparent slits (14 A-C) on the other photomask. Simulantaneous detection of the beams by photodetectors (18 A-C) indicates alignment. A method for obtaining precise centering by scanning the slits with the beams, sampling light transmitted through the slits, and fitting the samples to a parabola by the use of a computer (27) is also described.
Inventors
- 👤 George T. Harvey
- 👤 Laurence S. Watkins
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 21:35
CPC Classifications
G; G03; G03F; G03F9/00; G03F9/70; G03F9/7073; G03F9/7076; H; H10; H10P; H10P72/00; H10P72/50; H10P72/57
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
193 words
A method for aligning first and second planar members, comprising the step of forming first and second light confining elements in the first planar member, forming first and second transparent openings, each of smaller width than length, in the second member so as to be approximately aligned, respectively, with the first and second light confining elements, locating first and second photodetectors, respectively, adjacent the first and second openings and opposite the first planar member, directing a first light beam through the first light confining member toward the second planar member, direction a second light beam through the second light confining member toward the second member, causing the first beam to scan the first opening in a direction traverse to the width of the first opening, causing the second beam to scan the second opening in a direction traverse to the width of the second opening, and causing movement of the second member relative to the first member until the first beam is transmitted through the first opening and is detected by the first light detector and the second light beam is simultaneously transmitted through the second opening and detected by the second detector.
Claim 2
Independent Claim
193 words
A method for aligning first and second planar members, comprising the step of forming first and second light confining elements in the first planar member, forming first and second transparent openings, each of smaller width than length, in the second member so as to be approximately aligned, respectively, with the first and second light confining elements, locating first and second photodetectors, respectively, adjacent the first and second openings and opposite the first planar member, directing a first light beam through the first light confining member toward the second planar member, direction a second light beam through the second light confining member toward the second member, causing the first beam to scan the first opening in a direction traverse to the width of the first opening, causing the second beam to scan the second opening in a direction traverse to the width of the second opening, and causing movement of the second member relative to the first member until the first beam is transmitted through the first opening and is detected by the first light detector and the second light beam is simultaneously transmitted through the second opening and detected by the second detector.
Claim 3
Dependent Claim
13 words
The method of claim 1 wherein the light confining elements are zone plates.
Claim 4
Dependent Claim
25 words
The method of claim 1 wherein the second planar member is aligned with respect to the first member within tolerances of less than 1 micron.
Claim 5
Dependent Claim
41 words
The method of claim 1 wherein the first light beam originates at a first light source that is fixed to the first planar member and the second light beam originates at a second light source fixed to the first planar member.
Claim 6
Dependent Claim
18 words
The method of claim 4 wherein the first and second light sources are both sources of collimated light.
Claim 7
Independent Claim
163 words
A method for aligning first and second members comprising the step of forming at least a first zone plate in a first planar member, forming at least a first transparent opening in the second member so as to be aligned with the first zone plate, locating at least a first photodetector adjacent the first opening and opposite the first planar member, directing at least a first light beam through the first zone plate toward the second member, moving the second member relative to the first member so as to cause the first light beam to scan the width of the first opening, making three equally-spaced measurements of light intensity through the first opening, after each scan changing the location of the initiation of the successive scan until two of the three measurements are substantially equal and the three measurements of light intensity vs. distance each substantially describe a parabola, and the parabola is used to center the first opening on the first beam.
Claim 8
Independent Claim
163 words
A method for aligning first and second members comprising the step of forming at least a first zone plate in a first planar member, forming at least a first transparent opening in the second member so as to be aligned with the first zone plate, locating at least a first photodetector adjacent the first opening and opposite the first planar member, directing at least a first light beam through the first zone plate toward the second member, moving the second member relative to the first member so as to cause the first light beam to scan the width of the first opening, making three equally-spaced measurements of light intensity through the first opening, after each scan changing the location of the initiation of the successive scan until two of the three measurements are substantially equal and the three measurements of light intensity vs. distance each substantially describe a parabola, and the parabola is used to center the first opening on the first beam.
Claim 9
Dependent Claim
151 words
The method of claim 6 further comprising the step of forming a second zone plate in the first member, forming a second transparent opening in the second member so as to be aligned with the second zone plate, locating a second photodetector adjacent the second opening and opposite the first member, directing a second light beam through the second zone plate toward the second planar member, and moving the second member relative to the first member to cause the second light beam to scan the width of the second opening, making three equally-spaced measurements of light intensity through the second opening, after each scan changing the location of the initiation of the successive scan until two of the three measurements are substantially equal and the three measurements of light intensity vs. distance each substantially describe a parabola, and the parabola is used to center the second opening on the second beam.
Claim 10
Independent Claim
194 words
A method for aligning first and second planar members comprising the steps of forming first and second zone plates in the first planar member, forming first and second transparent openings in the second member so as to be approximately aligned, respectively, with the first and second zone plates, locating first and second photodetectors, respectively, adjacent the first and second openings and opposite the first planar member, directing a first light beam through the first zone plate toward the second planar member, directing a second light beam through the second zone plate toward the second member, causing the first and second light beams to make a plurality of scans of the widths of the first and second openings, making three equally-spaced measurements of light intensity through each opening, after each scan, changing the location of the initiation of the successive scan and the angular orientation of the second planar member until two of the three measurements are substantially equal and the three measurements of light intensity vs. distance each substantially describe a parabola, and using the parabolas to center, respectively, the first opening on the first beam and the second opening on the second beam.
Claim 11
Independent Claim
194 words
A method for aligning first and second planar members comprising the steps of forming first and second zone plates in the first planar member, forming first and second transparent openings in the second member so as to be approximately aligned, respectively, with the first and second zone plates, locating first and second photodetectors, respectively, adjacent the first and second openings and opposite the first planar member, directing a first light beam through the first zone plate toward the second planar member, directing a second light beam through the second zone plate toward the second member, causing the first and second light beams to make a plurality of scans of the widths of the first and second openings, making three equally-spaced measurements of light intensity through each opening, after each scan, changing the location of the initiation of the successive scan and the angular orientation of the second planar member until two of the three measurements are substantially equal and the three measurements of light intensity vs. distance each substantially describe a parabola, and using the parabolas to center, respectively, the first opening on the first beam and the second opening on the second beam.
References Cited (Backward Citations)
US4037969A
Cited
US4761561A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-02-26 | 1993-08-28 | 1994-02-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-02-26 | 1997-08-28 | 1998-02-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-02-26 | 2001-08-28 | 2002-02-27 | $7700.00 | Window Closed / Lapsed |