US4220706A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Etchant solution containing HF-HnO3 -H2 SO4 -H2 O2
Assignee: RCA Corp
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Filing: 1978-05-10
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Granted: 1980-09-02
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Expires: 1998-05-10
Abstract
Abstract An etchant solution for multilayered metal layers comprising an aqueous solution of from 0.5 to 50 percent by weight of nitric acid, from 0.03 to 1.0 percent by weight of hydrofluoric acid, from 0.05 to 0.5 percent by weight of hydrogen peroxide and from 0.1 to 1.0 percent by weight of sulphuric acid. The solution is compatible with photolithographic techniques and uniformly etches three or more metals.
Inventors
- 👤 Mark A. Spak
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 20:46
CPC Classifications
H; H10; H10P; H10P50/00; H10P50/60; H10P50/66; H10P50/663; H10P50/667; C; C23; C23F; C23F1/00; C23F1/10; C23F1/14; C23F1/16; C23F1/18; C23F1/20; C23F1/26; C23F1/28; H10D; H10D64/00; H10D64/01; H10D64/011
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
105 words
A method of etching three or more metal layers on a silicon-containing substrate using a single etchant which comprises applying a photoresist over the metal layers, exposing the photoresist through a mask, developing the photoresist to reveal portions of the metal layers and immersing the wafer in an etchant solution comprising from about 0.5 to 50 percent by weight of nitric acid, from about 0.03 to 1 percent by weight of hydrofluoric acid, from about 0.05 to 0.5 percent by weight of hydrogen peroxide and from about 0.1 to 1.0 percent by weight of sulphuric acid until the metal not covered by photoresist has dissolved.
Claim 2
Independent Claim
105 words
A method of etching three or more metal layers on a silicon-containing substrate using a single etchant which comprises applying a photoresist over the metal layers, exposing the photoresist through a mask, developing the photoresist to reveal portions of the metal layers and immersing the wafer in an etchant solution comprising from about 0.5 to 50 percent by weight of nitric acid, from about 0.03 to 1 percent by weight of hydrofluoric acid, from about 0.05 to 0.5 percent by weight of hydrogen peroxide and from about 0.1 to 1.0 percent by weight of sulphuric acid until the metal not covered by photoresist has dissolved.
Claim 3
Dependent Claim
60 words
A method according to claim 1 wherein said metal layers comprise a first layer of aluminum from about 0.1 to 8 microns thick; a second layer of titanium, molybdenum or tungsten from about 0.2 to 0.7 micron thick; and a third layer selected from the group consisting of nickel and copper or both from about 0.4 to 2 microns thick.
Claim 4
Dependent Claim
30 words
A method according to claim 1 wherein said silicon-containing substrate is selected from the group consisting of silicon, doped silicon, polycrystalline silicon, oxygen-doped polycrystalline silicon, silicon oxide and silicon nitride.
Claim 5
Dependent Claim
33 words
A method according to claim 1 wherein the substrate is a silicon wafer, the metal layers are aluminum about 3 microns thick, titanium about 0.3 micron thick and nickel about 0.7 micron thick.
Claim 6
Dependent Claim
41 words
A method according to claim 1 wherein the substrate is a polycrystalline, oxygen doped silicon over a doped silicon wafer and the metal layers are aluminum about 3 microns thick, titanium about 0.3 micron thick and nickel about 0.7 micron thick.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-09-02 | 1984-03-03 | 1984-09-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-09-02 | 1988-03-03 | 1988-09-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-09-02 | 1992-03-03 | 1992-09-02 | $7700.00 | Window Closed / Lapsed |