US3607480A
Expired / Lapsed
US
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Process for etching composite layered structures including a layer of fluoride-etchable silicon nitride and a layer of silicon dioxide
Assignee: Texas Instruments Inc
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Filing: 1968-12-30
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Granted: 1971-09-21
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Expires: 1988-12-30
Abstract
Abstract A single etchant process for etching a composite layered structure of silicon nitride and silicon dioxide. Hydrogen and fluoride ion-containing aqueous etching solutions, such as hydrofluoric acid having a concentration of less than approximately 2 percent by weight, and other equivalent solutions including ammonium fluoride and ammonium bifluoride solutions and fluosilicic acid, are applied to the structure while the temperature is maintained below the boiling point of these solutions, whereby the rate of etching of the silicon nitride is substantially equal to the rate of etching of the silicon dioxide.
Inventors
- 👤 Victor Harrap
- 👤 Harold Gary Carlson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 16:54
CPC Classifications
H; H10; H10P; H10P76/00; H10P76/40; H10P50/00; H10P50/20; H10P50/28; H10P50/282; H10P50/283; Y; Y10; Y10S; Y10S148/00; Y10S148/043; Y10S148/051; Y10S148/106
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
14 words
A process as set forth in claim 1 wherein said solution comprises hydrofluoric acid.
Claim 2
Dependent Claim
17 words
A process as set forth in claim 1 wherein said solution comprises a solution of ammonium bifluoride.
Claim 3
Dependent Claim
17 words
A process as set forth in claim 1 wherein said solution comprises a solution of ammonium fluoride.
Claim 4
Dependent Claim
14 words
A process as set forth in claim 1 wherein said solution comprises fluosilicic acid.
Claim 5
Dependent Claim
48 words
A process as set forth in claim 1 wherein said concentration is between approximately 0.07 percent and 0.7 percent by weight and the temperature is maintained between approximately 60* C. and 96* C. whereby the rates of etching the silicon nitride and the silicon dioxide are substantially equal.
Claim 6
Dependent Claim
24 words
A process as set forth in claim 6 wherein said concentration is approximately 0.3 percent and the temperature is maintained at approximately 90* C.
Claim 7
Dependent Claim
27 words
A process as set forth in claim 6 wherein said concentration is maintained at a substantially constant level by adding water to replace that lost by evaporation.
Claim 8
Dependent Claim
115 words
A process for producing apertures in composite layered structures including a layer of amorphous silicon nitride and a layer of silicon dioxide on a silicon substrate comprising forming a mask over the surface of the structure, and applying thereto an aqueous etching solution containing hydrogen and fluoride ions and having a fluoride ion concentration equivalent to that of an aqueous solution of hydrogen fluoride with a concentration of less than approximately 2 percent by weight while maintaining the temperature below the boiling point of the solution, said mask being resistant to etching by the solution, for a time sufficient to achieve etching of both layers, whereby both layers are etched at substantially the same rate.
Claim 9
Dependent Claim
14 words
A process as set forth in claim 9 wherein said solution comprises hydrofluoric acid.
Claim 10
Dependent Claim
17 words
A process as set forth in claim 9 wherein said solution comprises a solution of ammonium bifluoride.
Claim 11
Dependent Claim
17 words
A process as set forth in claim 9 wherein said solution comprises a solution of ammonium fluoride.
Claim 12
Dependent Claim
14 words
A process as set forth in claim 9 wherein said solution comprises fluosilicic acid.
Claim 13
Dependent Claim
27 words
A process as set forth in claim 9 wherein said between about 0.07 percent and 0.7 percent and the temperature between about 60* C. and 96* C.
Claim 14
Dependent Claim
33 words
A process as set forth in claim 9 wherein said mask is formed of a metallic material which is etchable by a material which will not significantly attack silicon nitride and silicon dioxide.
Claim 15
Dependent Claim
44 words
A process as set forth in claim 15 wherein said mask if formed of a metallic material selected from the group consisting of molybdenum, platinum, tungsten and nichrome, and wherein said temperature is approximately 90* C. and the acid concentration is approximately 0.3 percent.
Claim 16
Dependent Claim
27 words
A process as set forth in claim 16 wherein said acid concentration is maintained at approximately 0.3 percent by adding water to replace that lost by evaporation.
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) | 1974-09-20 | 1975-03-22 | 1975-09-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-20 | 1979-03-22 | 1979-09-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-20 | 1983-03-22 | 1983-09-21 | $7700.00 | Window Closed / Lapsed |