Patent US4481071A successfully refreshed from Google Patents.
US4481071A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process of lift off of material
Assignee: International Business Machines Corp
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Filing: 1983-12-29
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Granted: 1984-11-06
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Expires: 2003-12-29
Abstract
Abstract Process for lift-off fabrication of sputtered dielectric or nonmagnetic gap materials and thin-film heads for either a single-element thin-film head or side-by-side elements on a thin-film head. The lift-off process utilizes a copper coating that is removed by a twenty percent solution of ammonium persulfate with a pH in the range of seven to nine to assure complete removal of gap material from the back closure of the thin-film head without damage to the underlying permalloy. The process can also be utilized to obtain a multiple layer deposits on a single thin-film had by repeating the steps of the process. The process provides for a clean hole, no dielectric on the surface nor any attacking on the magnetic material.
Inventors
- 👤 Nathaniel C. Anderson
- 👤 Robert B. Chesnut
- 👤 Larry E. Daby
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 09:53
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/48; G11B5/488; C; C23; C23F; C23F1/00; C23F1/10; C23F1/14; G11B5/127; G11B5/31; G11B5/3163; H; H01; H01F; H01F41/00; H01F41/32; H01F41/34; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/4902; Y10T29/49021; Y10T29/49032; Y10T29/49036; Y10T29/49043; Y10T29/49044
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
95 words
The process for fabrication of thin film magnetic transducer gaps by lift-off basic process comprising: a. sputter depositing a thin copper metalization layer; b. applying a non-conductive mask to predetermined selected portions of a surface of said metalization layers; c. plating copper on unmasked surfaces to a thickness at least twice the thickness of the desired gap and removing said non-conductive mask; d. sputter etching for removing said exposed metalization layer; e. sputter deposition of dielectric material; and, f. etching away said plated copper and remaining metalization layer material with a solution of ammonium persulfate.
Claim 2
Dependent Claim
95 words
The process for fabrication of thin film magnetic transducer gaps by lift-off basic process comprising: a. sputter depositing a thin copper metalization layer; b. applying a non-conductive mask to predetermined selected portions of a surface of said metalization layers; c. plating copper on unmasked surfaces to a thickness at least twice the thickness of the desired gap and removing said non-conductive mask; d. sputter etching for removing said exposed metalization layer; e. sputter deposition of dielectric material; and, f. etching away said plated copper and remaining metalization layer material with a solution of ammonium persulfate.
Claim 3
Dependent Claim
22 words
The process of claim 1 wherein said ammonium persulfate, (NH 4 ) 2 S 2 O 8 is a twenty percent solution.
Claim 4
Dependent Claim
24 words
The process of claim 1 wherein said ammonium persulfate (NH 4 ) 2 S 2 O 8 is a 10 to 20 percent solution.
Claim 5
Dependent Claim
18 words
The process of claim 3 wherein said solution has a pH in the range of 7 to 9.
Claim 6
Dependent Claim
18 words
The process of claim 3 wherein said solution further comprises chloride ions less than 100 parts per million.
Claim 7
Dependent Claim
39 words
The process of claim 3 wherein said solution further comprises a range selected from the group of sodium chloride, calcium chloride, ammonium chloride and potassium chloride in a concentration to provide chloride ions of about 100 parts per million.
Claim 8
Dependent Claim
24 words
The process of claim 1 wherein multiple cycles of said process are involved to produce transducers with varying gap thicknesses on a single substrate.
References Cited (Backward Citations)
US4119483A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-11-06 | 1988-05-07 | 1988-11-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-11-06 | 1992-05-07 | 1992-11-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-11-06 | 1996-05-07 | 1996-11-06 | $7700.00 | Window Closed / Lapsed |