US3906133A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Nitrocellulose protective coating on masks used in IC manufacture
Assignee: Harris Corp
•
Filing: 1974-04-23
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Granted: 1975-09-16
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Expires: 1994-04-23
Abstract
Abstract A photomask used in making integrated circuits consisting of a transparent substrate, such as glass having an iron oxide layer, is coated with nitrocellulose to protect said layer. The nitrocellulose coating prevents damage to the iron oxide layer caused by protuberances or dendrites projecting through the photoresist layer on a silicon wafer in contact with the photomask, and prevents sticking between the photoresist and the iron oxide.
Inventors
- 👤 Richard E Flutie
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 15:10
CPC Classifications
G; G03; G03F; G03F1/00; G03F1/38; G03F1/48; Y; Y10; Y10S; Y10S438/00; Y10S438/942; Y10T; Y10T428/00; Y10T428/24; Y10T428/24479; Y10T428/24612; Y10T428/24802; Y10T428/24851; Y10T428/24868
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
99 words
IN A COMBINATION USEFUL IN THE PRODUCTION OF INTEGRATED CIRCUITS BY A PHOTOLITHOGRAPHIC PROCESS, A SILICON WAFER, A PHOTORESIST COATING ON SAID WAFER SAID WAFER HAVING DENDRITES OR PROTUBERANCES PROJECTING ABOVE THE PHOTORESIST SURFACE, A PHOTOMASK COMPRISING A TRANSPARENT SUBSTRATE MEMBER HAVING A HARD MASKING LAYER THEREON, A THIN COATING OF NITROCELLULOSE ON SAID MASKING LAYER, THE THICKNESS OF SAID NITROCELLULOSE COATING BEING FROM SLIGHTLY LESS TO AT LESS SLIGHTLY MORE THAN THE HEIGHT OF THE LONGEST DENDRITE OR PROTUBERANCE PROJECTING ABOVE THE PHOTORESIST LAYER ON THE SILICON WAFER AND THE SAID NITROCELLULOSE COATING CONTACTING THE SAID PHOTORESIST LAYER.
Claim 2
Dependent Claim
99 words
IN A COMBINATION USEFUL IN THE PRODUCTION OF INTEGRATED CIRCUITS BY A PHOTOLITHOGRAPHIC PROCESS, A SILICON WAFER, A PHOTORESIST COATING ON SAID WAFER SAID WAFER HAVING DENDRITES OR PROTUBERANCES PROJECTING ABOVE THE PHOTORESIST SURFACE, A PHOTOMASK COMPRISING A TRANSPARENT SUBSTRATE MEMBER HAVING A HARD MASKING LAYER THEREON, A THIN COATING OF NITROCELLULOSE ON SAID MASKING LAYER, THE THICKNESS OF SAID NITROCELLULOSE COATING BEING FROM SLIGHTLY LESS TO AT LESS SLIGHTLY MORE THAN THE HEIGHT OF THE LONGEST DENDRITE OR PROTUBERANCE PROJECTING ABOVE THE PHOTORESIST LAYER ON THE SILICON WAFER AND THE SAID NITROCELLULOSE COATING CONTACTING THE SAID PHOTORESIST LAYER.
Claim 3
Dependent Claim
27 words
The article of claim 1 wherein the nitrocellulose coating is slightly less than the height of said longest dendrite and is less than 75 microns in thickness.
Claim 4
Dependent Claim
31 words
The article of claim 1 wherein the nitrocellulose coating is at most about slightly more than the height of said longest dendrite and is slightly more than 75 microns in thickness.
Claim 5
Dependent Claim
26 words
The article of claim 2 wherein the substrate member is glass, and the nitrocellulose coating is in contact with the photoresist layer in the silicon wafer.
Claim 6
Dependent Claim
26 words
The article of claim 3 wherein the substrate member is glass, and the nitrocellulose coating is in contact with the photoresist layer in the silicon wafer.
Claim 7
Dependent Claim
12 words
The article of claim 4 wherein the hard photomask layer comprises chromium.
Claim 8
Dependent Claim
13 words
The article of claim 4 wherein the hard photomask layer comprises chromium oxide.
Claim 9
Dependent Claim
12 words
The article of claim 4 wherein the hard photomask comprises iron oxide.
Claim 10
Dependent Claim
12 words
The article of claim 5 wherein the hard photomask layer comprises chromium.
Claim 11
Dependent Claim
13 words
The article of claim 5 wherein the hard photomask layer comprises chromium oxide.
Claim 12
Dependent Claim
13 words
The article of claim 5 wherein the hard photomask layer comprises iron oxide.
Claim 13
Dependent Claim
114 words
IN THE PRODUCTION OF INTEGRATED CIRCUITS BY A PHOTOLITHOGRAPHIC PROCESS COMPRISING THE STEP OF COATING A SILICON WAFER WITH A PHOTORESIST FORMING A PHOTOMASK ON A TRANSPARENT SUBSTRATE COATING SAID PHOTOMASK WITH A HARD MASKING LAYER, AND PLACING SAID PHOTORESIST IN JUXTAPOSITION WITH SAID HARD MASKING LAYER THE IMPROVEMENT WHICH COMPRISES: COATING THE MASKING LAYER WITH A THIN LAYER OF NITROCELLULOSE HAVING A THICKNESS OF FROM SLIGHTLY LESS TO AT LEAST SLIGHTLY MORE THAN THE HEIGHT OF DENDRITES OR PROTUBERANCES ON THE SILICON WAFER PROJECTING ABOVE THE PHOTORESIST AND PLACING THE PHOTORESIST LAYER IN DIRECT CONTACT WITH SAID LAYER OF NITROCELLULOSE ON THE MASKING LAYER WHEREBY SCRATCHING OF THE MASKING LAYER IN SUBSTANTIALLY PREVENTED.
Claim 14
Dependent Claim
114 words
IN THE PRODUCTION OF INTEGRATED CIRCUITS BY A PHOTOLITHOGRAPHIC PROCESS COMPRISING THE STEP OF COATING A SILICON WAFER WITH A PHOTORESIST FORMING A PHOTOMASK ON A TRANSPARENT SUBSTRATE COATING SAID PHOTOMASK WITH A HARD MASKING LAYER, AND PLACING SAID PHOTORESIST IN JUXTAPOSITION WITH SAID HARD MASKING LAYER THE IMPROVEMENT WHICH COMPRISES: COATING THE MASKING LAYER WITH A THIN LAYER OF NITROCELLULOSE HAVING A THICKNESS OF FROM SLIGHTLY LESS TO AT LEAST SLIGHTLY MORE THAN THE HEIGHT OF DENDRITES OR PROTUBERANCES ON THE SILICON WAFER PROJECTING ABOVE THE PHOTORESIST AND PLACING THE PHOTORESIST LAYER IN DIRECT CONTACT WITH SAID LAYER OF NITROCELLULOSE ON THE MASKING LAYER WHEREBY SCRATCHING OF THE MASKING LAYER IN SUBSTANTIALLY PREVENTED.
Claim 15
Dependent Claim
38 words
The method of claim 12 wherein the hard masking layer is coated with nitrocellulose by the steps comprising evenly distributing a solution of nitrocellulose over the surface of the masking layer and evaporating the solvent from said solutions.
Claim 16
Dependent Claim
13 words
The method of claim 12 wherein the hard masking layer comprises iron oxide.
Claim 17
Dependent Claim
12 words
The method of claim 12 wherein the hard masking layer comprises chromium.
Claim 18
Dependent Claim
13 words
The method of claim 12 wherein the hard masking layer comprises chromium oxide.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-15 | 1979-03-17 | 1979-09-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-15 | 1983-03-17 | 1983-09-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-15 | 1987-03-17 | 1987-09-16 | $7700.00 | Window Closed / Lapsed |