US4886569A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Plasma etching process
Assignee: Nortel Networks Ltd
•
Filing: 1989-02-21
•
Granted: 1989-12-12
•
Expires: 2009-02-21
Abstract
Abstract A polysilicon layer or a single crystal silicon substrate is plasma etched in a two staged process. The first stage was a non-selective anisotropic etch to define a desired pattern by etching part way through the polysilicon. The second stage was a selective etch to secure remaining polysilicon and expose the substrate.
Inventors
- 👤 Sureshchandra M. Ojha
- 👤 Stephen R. Jennings
- 👤 Anthony D. Johnston
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 10:17
CPC Classifications
H; H10; H10P; H10P50/00; H10P50/20; H10P50/26; H10P50/264; H10P50/266; H10P50/267; H10P50/268
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
96 words
A process for selectively etching a polysilicon layer provided on a single crystal substrate, the method including masking the layer, exposing the unmasked regions of the layer to a first non-selective anisotropic plasma etch comprising sulphur hexafluoride (SF 6 ) containing at least 20 volume percent of oxygen whereby a major portion of exposed polysilicon is removed, exposing the structure to a second selective isotropic plasma etch comprising sulphur hexafluoride or a mixture of sulphur hexafluoride and a trace quantity of oxygen whereby the remaining polysilicon is removed without significant attack of the single crystal substrate.
Claim 2
Dependent Claim
96 words
A process for selectively etching a polysilicon layer provided on a single crystal substrate, the method including masking the layer, exposing the unmasked regions of the layer to a first non-selective anisotropic plasma etch comprising sulphur hexafluoride (SF 6 ) containing at least 20 volume percent of oxygen whereby a major portion of exposed polysilicon is removed, exposing the structure to a second selective isotropic plasma etch comprising sulphur hexafluoride or a mixture of sulphur hexafluoride and a trace quantity of oxygen whereby the remaining polysilicon is removed without significant attack of the single crystal substrate.
Claim 3
Dependent Claim
22 words
A process as claimed in claim 1, wherein said first etching stage is performed at a pressure of 0.4 to 1.0 torr.
Claim 4
Dependent Claim
22 words
A process as claimed in claim 2 wherein the second etching stage is performed at a pressure of 0.8 to 3.0 torr.
Claim 5
Dependent Claim
21 words
A process as claimed in claim 3 wherein the substrate comprises an integrated circuit incorporating both bipolar and field effect transistors.
References Cited (Backward Citations)
US4457820A
Cited
US4528066A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-12-11 | 1993-06-12 | 1993-12-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-12-11 | 1997-06-12 | 1997-12-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-12-11 | 2001-06-12 | 2001-12-12 | $7700.00 | Window Closed / Lapsed |