Patent US2244300A successfully refreshed from Google Patents.
US3596348A
Expired / Lapsed
US
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Thyristors and other semiconductor devices
Assignee: ZF International UK Ltd
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Filing: 1969-03-04
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Granted: 1971-08-03
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Expires: 1989-03-04
Abstract
Abstract Thyristors are produced starting with an N-type wafer and forming P-type layers on opposite sides to act as the anodes and gates of the thyristors. N-type layers acting as the cathodes are then produced in or on the plate layers, after which the wafer is coated with nickel and then with gold, and gold is removed from at least part of the portion of each gate-cathode junction which is exposed in the surface of the wafer. The wafer is then divided into chips by cracking or sawing, and the cracked or sawn junctions are then improved by etching, the etching at the same time removing the nickel from the junctions exposed by the removal of the gold. A similar process is applied to manufacture transistors.
Inventors
- 👤 Michael Albert Stacey
- 👤 Michael Searle
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 00:26
CPC Classifications
H; H10; H10P; H10P95/00; H10D; H10D99/00; H10P14/00; H10P14/40; H10P14/46
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
168 words
A method of manufacturing thyristors, including the following steps: a. forming in or on opposite sides of an N-type wafer P-type layers which are to act as the anodes and the gates respectively of a plurality of thyristors. b. forming in or on the gate layers a plurality of N-type layers which are to act as the cathodes of the plurality of thyristors respectively, c. plating the wafer first with nickel and then with gold, d. removing the gold from at least part of the portion of each gate-cathode junction which is exposed at the surface of the wafer, e. dividing the wafer into a plurality of NPNP chips either by scribing and cracking or by sawing, f. etching the junctions between the original N-type wafer and the anodes and gates of each chip using an etchant which does not remove the gold but does remove the nickel from the gate-cathode junction of each chip, g. making contacts to the gold layers on the anode, cathode and gate.
Claim 2
Dependent Claim
23 words
A method as claimed in claim 2 in which step (b) is carried out by diffusion of N-type material selectively through a mask.
Claim 3
Dependent Claim
33 words
A method as claimed in claim 2 in which step (b) is carried out by diffusing N-type material into the P-type gate layer and then selectively etching to produce the required N-type layers.
Claim 4
Dependent Claim
24 words
A method as claimed in claim 1 including the step of increasing the P-concentration of the P-type gate layer between steps (b) and (c).
Claim 5
Independent Claim
164 words
A method of manufacturing transistors, including the following steps: a. forming in or on one side of a P-type wafer which is to act as the base of each transistor an N-type layer which is to act as the collector of each transistor, b. forming in or on the other side of the P-type wafer a plurality of N-type layers which are to act as the emitters of the plurality of transistors respectively, c. plating the wafer first with nickel and then with gold, d. removing the gold from at least part of the portion of each base-emitter junction which is exposed at the surface of the wafer, e. dividing the wafer into a plurality of NPN chips either by scribing and cracking or by sawing, f. etching the base-collector junctions using an etchant which does not remove gold but does remove the nickel from the base-emitter junction of each chip, g. making contacts to the gold layers on the base, collector and emitter.
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) | 1974-08-02 | 1975-02-01 | 1975-08-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-02 | 1979-02-01 | 1979-08-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-02 | 1983-02-01 | 1983-08-03 | $7700.00 | Window Closed / Lapsed |