US4142953A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Semiconductor etching
Assignee: ITT Inc
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Filing: 1978-03-30
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Granted: 1979-03-06
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Expires: 1998-03-30
Abstract
Abstract KOH can be used as the electrolyte for self-limiting etching of GaAs to preferentially remove p-type material from n-type material but does not work with GaAlAs because etching is halted by the precipitation of aluminium hydroxide. An aqueous solution of triethanolamine has been found to be an alternative electrolyte which does not suffer from this problem. Preferably no external drive voltage is used but instead the current flow is promoted by the e.m.f. developed by the etching cell itself.
Inventors
- 👤 David F. Lovelace
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 01:50
CPC Classifications
C; C25; C25F; C25F7/00; C25F3/00; C25F3/02; C25F3/12; H; H10; H10P; H10P50/00; H10P50/60; H10P50/61; H10P50/617
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
109 words
A method of electrochemical self-limiting etching of a workpiece of semiconductive material consisting of gallium arsenide and/or one or more of its solid solutions with other elements selected from Groups III and V of the Periodic Table, which workpiece contains an exposed region of p-type material backed by n-type material, wherein the workpiece is made one electrode of an electrochemical cell whose other electrode is made of platinum and whose electrolyte is provided by an aqueous solution of tri-ethanolamine, and wherein during the etching the workpiece its surface is protected from exposure to radiation of short enough wavelength to give rise to the generation thereat of photon-excited electron-hole pairs.
Claim 2
Independent Claim
109 words
A method of electrochemical self-limiting etching of a workpiece of semiconductive material consisting of gallium arsenide and/or one or more of its solid solutions with other elements selected from Groups III and V of the Periodic Table, which workpiece contains an exposed region of p-type material backed by n-type material, wherein the workpiece is made one electrode of an electrochemical cell whose other electrode is made of platinum and whose electrolyte is provided by an aqueous solution of tri-ethanolamine, and wherein during the etching the workpiece its surface is protected from exposure to radiation of short enough wavelength to give rise to the generation thereat of photon-excited electron-hole pairs.
Claim 3
Dependent Claim
16 words
A method as claimed in claim 1 wherein the workpiece is made of gallium aluminium arsenide.
Claim 4
Dependent Claim
23 words
A method as claimed in claim 1 and 2 wherein the electrolyte is directed against the workpiece in a jet by a pump.
Claim 5
Dependent Claim
18 words
A method as claimed in claim 3 wherein the platinum electrode is located in the jet of electrolyte.
Claim 6
Dependent Claim
18 words
A method as claimed in claim 1 wherein the electrolyte includes a dissolved salt enhancing its electrical conductivity.
Claim 7
Dependent Claim
26 words
A method as claimed in claim 1 wherein the drive voltage for the electrochemical etching is provided by the voltage developed by the electrochemical cell itself.
Claim 8
Dependent Claim
25 words
A method as claimed in claim 6 wherein an external voltage source is used to back-off part of the voltage developed by the electrochemical cell.
References Cited (Backward Citations)
US3251757A
Cited
US3184399A
Cited
US3421987A
Cited
US3413205A
Cited
US3791948A
Cited
US3959098A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-03-05 | 1982-09-04 | 1983-03-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-03-05 | 1986-09-04 | 1987-03-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-03-05 | 1990-09-04 | 1991-03-06 | $7700.00 | Window Closed / Lapsed |