Patent US3647445A successfully refreshed from Google Patents.
US3647445A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Step and repeat photomask and method of using same
Assignee: Texas Instruments Inc
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Filing: 1969-10-24
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Granted: 1972-03-07
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Expires: 1989-10-24
Abstract
Abstract A method is described for exposing a layer of photoresist so as to eliminate the defects which would otherwise be caused by a defective photomask. The method utilizes a unique mask in which the repetitive opaque patterns are identical except that the patterns in alternate rows are slightly larger than the patterns in the other alternate rows. The photomask is aligned with the photoresist in the usual manner and the photoresist exposed. Then the photomask is indexed one row and the photoresist again exposed so that all areas of the photoresist are double exposed through different portions of the photomask, yet the edges of the unexposed areas are defined by a single exposure corresponding in size to the patterns in the rows which have the larger opaque areas.
Inventors
- 👤 Carmen D Burns
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 21:38
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/70; G03F7/70425; H; H10; H10P; H10P95/00
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
205 words
A method for photographically forming a protective mask which is substantially free of defects due to irregularities in the transparent regions of an exposure mask which is used to define the protective mask, the method consisting of the steps of: a. forming a layer of photosensitive material on the surface of a substrate; b. exposing said layer of photosensitive material to light through said exposure mask, said exposure mask having at least first and second patterns of transparent and opaque regions, said first and second patterns being related such that they are substantially identical in outline and orientation, except that said opaque regions in said second patterns are larger than the corresponding regions in said first pattern; c. repositioning said exposure mask with respect to said substrate and reexposing said layer of photosensitive material through said exposure mask thereby forming areas in said photosensitive layer which are unexposed, each of said unexposed areas being substantially symmetrically surrounded by an area which is single-exposed with the remainder of said photosensitive layer being double-exposed; and d. developing and selectively removing portions of said photosensitive layer thereby forming a protective mask which is substantially free of irregularities due to defects in the transparent regions of said exposure mask.
Claim 2
Dependent Claim
28 words
A method for photographically forming a protective mask in accordance with claim 2 wherein said exposure mask is in contact with said photosensitive layer during the exposure process.
Claim 3
Dependent Claim
32 words
A method of photographically forming a protective mask in accordance with claim 2 wherein said layer of photosensitive material is formed by coating a semiconductor substrate with photoresist and curing said photoresist.
Claim 4
Dependent Claim
34 words
A method for photographically forming a protective mask in accordance with claim 4 in which said semiconductor substrate is coated with an insulating layer prior to the formation of said layer of photosensitive material.
Claim 5
Dependent Claim
94 words
A mask for selectively exposing a photosensitive layer comprising: a. a transparent mask having first and second geometrically similar opaque patterns therein, said patterns being similarly oriented with respecT to at least one common axis, such that said photosensitive layer can be exposed such that first regions will not be exposed, second regions will be double exposed and third regions will be single-exposed by positioning said mask above said photosensitive layer, projecting light through said mask, indexing said mask with respect to said photosensitive layer and projecting light through said mask a second time.
Claim 6
Dependent Claim
41 words
The photomask of claim 6 wherein said first patterns comprise a first plurality of identical patterns and wherein said second pattern comprises a second plurality of identical patterns with said first and second patterns alternately repeating along at least one axis.
Claim 7
Dependent Claim
39 words
The photomask of claim 6 wherein said first pattern comprises a plurality of identical patterns, and wherein said second pattern comprises a plurality of identical patterns with said patterns alternately repeating along at least two axis of said photomask.
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) | 1975-03-07 | 1975-09-06 | 1976-03-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-07 | 1979-09-06 | 1980-03-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-07 | 1983-09-06 | 1984-03-07 | $7700.00 | Window Closed / Lapsed |