US3783520A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High accuracy alignment procedure utilizing moire patterns
Assignee: AT&T Inc
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Filing: 1972-08-01
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Granted: 1974-01-08
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Expires: 1992-08-01
Abstract
Abstract A pair of moire gratings that comprise a similar pattern of concentric lines but have a different pitch are used with a microscope to provide extremely accurate alignment of objects such as a photolithographic mask and a substrate of a semiconductive material.
Inventors
- 👤 M King
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:35
CPC Classifications
G; G03; G03F; G03F9/00; G03F9/70; G03F9/7049; G03F9/7073; G03F9/7076; H; H10; H10P; H10P95/00
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
113 words
A method of aligning two objects comprising the steps of: forming on the surface of the first object a first moire grating comprising an array of concentric regions having a substantially constant first pitch a; forming on the second object a second moire grating having a substantially constant second pitch b which is smaller than pitch a; aligning the first and second moire gratings so as to form a moire pattern comprising an array of concentric regions having a substantially constant third pitch c, where c a.b/ a- b ; and aligning one of the concentric regions of the moire pattern with a concentric region of either the first or second moire grating.
Claim 2
Independent Claim
113 words
A method of aligning two objects comprising the steps of: forming on the surface of the first object a first moire grating comprising an array of concentric regions having a substantially constant first pitch a; forming on the second object a second moire grating having a substantially constant second pitch b which is smaller than pitch a; aligning the first and second moire gratings so as to form a moire pattern comprising an array of concentric regions having a substantially constant third pitch c, where c a.b/ a- b ; and aligning one of the concentric regions of the moire pattern with a concentric region of either the first or second moire grating.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-01-07 | 1977-07-09 | 1978-01-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-07 | 1981-07-09 | 1982-01-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-07 | 1985-07-09 | 1986-01-08 | $7700.00 | Window Closed / Lapsed |