Patent US5176792A successfully refreshed from Google Patents.
US5176792A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for forming patterned tungsten layers
Assignee: Nokia Bell Labs
•
Filing: 1991-10-28
•
Granted: 1993-01-05
•
Expires: 2011-10-28
Abstract
Abstract The present applicants have discovered that a layer predominantly comprising tungsten can be formed into precise patterns having substantially vertical walls by using titanium as a mask and plasma etching in a fluorine-containing plasma such as CF 4 or SF 6 . The success of the process is believed attributable to the occurrence of an etch stop reaction on the sidewalls of the tungsten. The products of the reaction inhibit horizontal etching. After the tungsten is etched, the titanium mask can be selectively removed, as by etching in dilute HF. Each step in the process can be effected without subjecting the workpiece to voltage magnitudes in excess of 200 volts or temperatures outside the range between room temperature and 200° C.
Inventors
- 👤 Thomas R. Fullowan
- 👤 Stephen J. Pearton
- 👤 Fan Ren
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 09:22
CPC Classifications
C; C23; C23F; C23F4/00; H; H10; H10D; H10D64/00; H10D64/01; H10D64/011; H10P; H10P50/00; H10P50/20; H10P50/26; H10P50/264; H10P50/266; H10P50/267; H10P50/60; H10P50/66; H10P50/663; H10P50/667; H10P50/71
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
102 words
A method of forming a patterned tungsten contact to a gallium arsenide substrate comprising the steps of: depositing a layer predominantly comprising tungsten on said gallium arsenide substrate; forming on said tungsten layer a mask comprising titanium having a thickness of less than one micrometer; and removing the unmasked tungsten by reactive ion etching in a fluorine-containing plasma with a negative bias voltage of magnitude less than 200 volts applied between the substrate and the plasma during etching of the tungsten; and selectively removing the titanium mask relative to the underlying tungsten layer using an HF solution after etching the unmasked tungsten.
Claim 2
Independent Claim
102 words
A method of forming a patterned tungsten contact to a gallium arsenide substrate comprising the steps of: depositing a layer predominantly comprising tungsten on said gallium arsenide substrate; forming on said tungsten layer a mask comprising titanium having a thickness of less than one micrometer; and removing the unmasked tungsten by reactive ion etching in a fluorine-containing plasma with a negative bias voltage of magnitude less than 200 volts applied between the substrate and the plasma during etching of the tungsten; and selectively removing the titanium mask relative to the underlying tungsten layer using an HF solution after etching the unmasked tungsten.
Claim 3
Dependent Claim
13 words
The method of claim 1 wherein said tungsten is deposited by rf sputtering.
Claim 4
Dependent Claim
18 words
The method of claim 1 wherein said tungsten layer is masked with titanium by a lift off process.
Claim 5
Dependent Claim
22 words
The method of claim 1 wherein the unmasked tungsten is removed by reactive ion etching in an ambient comprising SF 6 .
Claim 6
Dependent Claim
22 words
The method of claim 1 wherein the unmasked tungsten is removed by reactive ion etching in an ambient comprising CF 4 .
Claim 7
Dependent Claim
25 words
The method of claim 1 wherein said reactive ion etching is effected in an ambient gas pressure in the range 1 mT to 140 mT.
References Cited (Backward Citations)
US5032538A
Cited
US4674174A
Cited
JPS6336547A
Cited
US4892835A
Cited
JPH01236622A
Cited
US4898804A
Cited
US4900398A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-01-05 | 1996-07-06 | 1997-01-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-01-05 | 2000-07-06 | 2001-01-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-01-05 | 2004-07-06 | 2005-01-05 | $7700.00 | Window Closed / Lapsed |