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Patent US3992235A successfully refreshed from Google Patents.
US3992235A
Expired / Lapsed
US
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Etching of thin layers of reactive metals
Assignee: AT&T Inc
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Filing: 1975-05-21
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Granted: 1976-11-16
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Expires: 1995-05-21
Abstract
Abstract Thin films of reactive metals in contact with layers of more noble metals, are etched by an etchant including a reactive cathodic inhibitor. The etchant is a hydrofluroric acid-based composition with hydrogen peroxide, a water soluble tetrazolium compound (the inhibitor) and a surface modifier, such as an alcohol or a more complex surfactant. For exemplary compositions, the undercutting of masking layers of noble metals or photolithographic materials is limited to the same order as the reactive metal film thickness.
Inventors
- 👤 Victor Charles Garbarini
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 23:05
CPC Classifications
C; C23; C23F; C23F1/00; C23F1/10; C23F1/14; C23F1/16; C23F1/26; H; H10; H10P; H10P50/00; H10P50/60; H10P50/66; H10P50/663; H10P50/667; H10W; H10W70/00; H10W70/01; H10W70/05
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
123 words
Method for the etching of a reactive metal layer comprising contacting a device precursor with an etchant wherein the device precursor includes a substrate, at least one partially exposed reactive metal layer and at least one noble metal layer in contact with the reactive metal layer, characterized in that the etchant is an aqueous solution consisting of 0.5 to 5 weight percent HF, 1 to 5 weight percent H 2 O 2 , 0.01 to 0.1 weight percent of a water soluble tetrazolium compound and a surface modifier, in which the etchant contains from 10 to 50 percent by volume of an alcohol, containing at least two carbons, as the surface modifier, whereby the exposed reactive metal is removed without excessive horizontal attack.
Claim 2
Dependent Claim
123 words
Method for the etching of a reactive metal layer comprising contacting a device precursor with an etchant wherein the device precursor includes a substrate, at least one partially exposed reactive metal layer and at least one noble metal layer in contact with the reactive metal layer, characterized in that the etchant is an aqueous solution consisting of 0.5 to 5 weight percent HF, 1 to 5 weight percent H 2 O 2 , 0.01 to 0.1 weight percent of a water soluble tetrazolium compound and a surface modifier, in which the etchant contains from 10 to 50 percent by volume of an alcohol, containing at least two carbons, as the surface modifier, whereby the exposed reactive metal is removed without excessive horizontal attack.
Claim 3
Dependent Claim
50 words
A method of claim 1 in which at least one of the reactive metal layers is situated between the substrate and the noble metal layer and in which the noble metal layer is so disposed as to leave a portion of the reactive metal layer exposed to the contacting etchant.
Claim 4
Dependent Claim
35 words
A method of claim 1 in which at least one of the reactive metal layers is situated above the noble metal layer, relative to the substrate, and is partially covered by a polymeric protective layer.
Claim 5
Dependent Claim
11 words
A method of claim 1 in which the alcohol is isopropanol.
Claim 6
Dependent Claim
12 words
A method of claim 1 in which the reactive metal is titanium.
Claim 7
Dependent Claim
14 words
A method of claim 1 in which the tetrazolium compound is triphenyl tetrazolium chloride.
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) | 1979-11-16 | 1980-05-17 | 1980-11-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-11-16 | 1984-05-17 | 1984-11-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-11-16 | 1988-05-17 | 1988-11-16 | $7700.00 | Window Closed / Lapsed |