Patent US2939671A successfully refreshed from Google Patents.
Patent US3871931A successfully refreshed from Google Patents.
US3871931A
Expired / Lapsed
US
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Method for selectively etching silicon nitride
Assignee: Plessey Inc
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Filing: 1974-01-17
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Granted: 1975-03-18
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Expires: 1994-01-17
Abstract
Abstract Etching of silicon nitride with a hot solution of arsenic acid is faster than the conventionally-employed phosphoric acid, and has the additional advantage of not attacking either silicon dioxide or heavily doped silicon. The invention is useful in the fabrication of silicon integrated circuits and in the surface treatment of silicon nitride bodies, i. e. chemical milling.
Inventors
- 👤 Geoffrey Allan Godber
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 12:27
CPC Classifications
C; C04; C04B; C04B41/00; C04B41/009; C04B41/53; C04B41/5338; C04B41/5353; C04B41/80; C04B41/91; H; H10; H10P; H10P50/00; H10P50/20; H10P50/28; H10P50/282; H10P50/283; Y; Y10; Y10S; Y10S148/00; Y10S148/043; Y10S148/051
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
36 words
A METHOD OF SELECTIVELY ETCHING SILICON NITRIDE COMPRISING: PROVIDING AN ETCH SOLUTION OF ARSENIC ACID, HEATING SAID ETCH SOLUTION OF AN ELEVATED TEMPERATURE; AND EXPOSING SELECTED AREAS OF SAID SILICON NITRIDE TO THE HEATED ETCH SOLUTION.
Claim 2
Independent Claim
36 words
A METHOD OF SELECTIVELY ETCHING SILICON NITRIDE COMPRISING: PROVIDING AN ETCH SOLUTION OF ARSENIC ACID, HEATING SAID ETCH SOLUTION OF AN ELEVATED TEMPERATURE; AND EXPOSING SELECTED AREAS OF SAID SILICON NITRIDE TO THE HEATED ETCH SOLUTION.
Claim 3
Dependent Claim
19 words
The method as claimed in claim 1, wherein said selected areas are defined by openings in an etch-resistant mask.
Claim 4
Dependent Claim
14 words
The method as claimed in claim 2, wherein said mask is a photo resist.
Claim 5
Dependent Claim
13 words
The method as claimed in claim 2, wherein said mask is silicon dioxide.
Claim 6
Dependent Claim
22 words
The method as claimed in claim 1, and additionally comprising adding a stabilizing arsenic compound to said etch solution prior to etching.
Claim 7
Dependent Claim
13 words
The method as claimed in claim 5, wherein said compound is arsenic pentoxide.
Claim 8
Dependent Claim
16 words
The method as claimed in claim 1, wherein said etch solution is heated to approximately 140*C.
Claim 9
Dependent Claim
23 words
In a method for the etching of silicon nitride by reaction thereof with a hot acid, the improvement comprising using hot arsenic acid.
Claim 10
Dependent Claim
23 words
In a method for the etching of silicon nitride by reaction thereof with a hot acid, the improvement comprising using hot arsenic acid.
Claim 11
Dependent Claim
15 words
The method as claimed in claim 8, wherein said arsenic acid is at about 140*C.
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) | 1978-03-17 | 1978-09-16 | 1979-03-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-17 | 1982-09-16 | 1983-03-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-17 | 1986-09-16 | 1987-03-18 | $7700.00 | Window Closed / Lapsed |