Patent US3811974A successfully refreshed from Google Patents.
US3811974A
Expired / Lapsed
US
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Silicon nitride-silicon oxide etchant
Assignee: Boeing North American Inc
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Filing: 1971-07-19
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Granted: 1974-05-21
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Expires: 1991-07-19
Abstract
Abstract THIS INVENTION DISCLOSES A CHEMICAL ETCHANT AND A PROCESS FOR CHEMICALLY ETCHING SILICON NITRIDE-SILICON OXIDE COMPOSITE STRUCTURES WHICH MAY BE USED, FOR EXAMPLE IN MICROELECTRONIC DEVICES. THE ETCHING PROCESS OR SYSTEM UTILIZES A MIXTURE OF PHOSPHORIC ACID AND A FLUOBORATE ANION CONTAINING COMPOUND SUCH AS FLUOROBIC ACID. THE ETCH RATE OF THE SILICON NITRIDE RELATIVE TO THE ETCH RATE OF THE SILICON OXIDE CAN BE CONTROLLED TO THE DESIRED ETCH RATE BY VARYING THE TEMPERATURE OF THE ETCHANT AND/OR ADJUSTING THE RATIO MIXTURE OF THE PHOSPHORIC ACID AND THE FLUOBORIC ACID.
Inventors
- 👤 J Rudmann
- 👤 A Squillace
- 👤 A Martin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 06:02
CPC Classifications
H; H10; H10P; H10P50/00; H10P50/20; H10P50/28; H10P50/282; H10P50/283
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-05-20 | 1977-11-19 | 1978-05-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-20 | 1981-11-19 | 1982-05-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-20 | 1985-11-19 | 1986-05-21 | $7700.00 | Window Closed / Lapsed |