Patent US2759173A successfully refreshed from Google Patents.
US3590477A
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Method for fabricating insulated-gate field effect transistors having controlled operating characeristics
Assignee: International Business Machines Corp
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Filing: 1968-12-19
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Granted: 1971-07-06
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Expires: 1988-12-19
Abstract
Abstract A method for fabricating electrical circuit components, field effect transistors, for example, in which the operating characteristics of the field effect devices are tailored by eliminating or passivating surface traps along the conduction channel. A layer of an active metal aluminum, for example, is deposited on the surface of an insulator, the latter being disposed in overlying relationship with the surface of a field effect transistor which has spaced source and drain regions. The active metal is disposed between the source and drain region. The transistor is subjected to heating for a time and temperature sufficient to passivate or eliminate surface traps. By heating for a temperature in a specified range, varying degrees of passivation can be attained. Heating in the absence of metallization does not alter the operating characteristics of the insulated gate field effect transistor.
Inventors
- 👤 George Cheroff
- 👤 Frederick Hochberg
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 21:02
CPC Classifications
H; H10; H10D; H10D84/00; H10D84/80; H10D84/82; H10D84/83; H10D99/00; Y; Y10; Y10S; Y10S438/00; Y10S438/91
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
39 words
The method of claim 1 wherein said wafer is formed of silicon, said insulating layer is silicon dioxide, and said active metal is one selected from the group consisting of aluminum (A1), silver (Ag), gold (Au), and molybdenum (Mo).
Claim 2
Dependent Claim
41 words
The method of claim 1 wherein said wafer is formed of silicon, said insulating layer is silicon dioxide, said thin metallic layer is aluminum, and said wafer is heated at a temperatUre between 250* C. and the aluminum-silicon dioxide eutetic temperature.
Claim 3
Dependent Claim
31 words
The method of claim 1 wherein said wafer is formed of silicon, said insulating layer is aluminum, and said wafer is heated at a temperature between 300* C. and 500* C.
Claim 4
Dependent Claim
19 words
The method of claim 1 wherein the step of heating includes the step of heating said wafer in air.
Claim 5
Dependent Claim
203 words
The method of claim 1 wherein the step of heating includes the step of heating said wafer in an inert atmosphere. A method for forming an insulated-gate field effect transistor which includes the steps of diffusing spaced portions of one conductivity type in a semiconductor wafer of opposite conductivity type, said spaced portions defining the source and drain diffusions, respectively, forming an insulating layer over surface portions of said wafer intermediate said spaced portions and defining a conducting channel therebetween, and providing electrical contacts to each of said spaced portions, and also a gate electrode over said insulating layer and registered with said conduction channel, the improvement comprising the step of subjecting said transistor to a heat-metallization process prior to said last-recited step for selectively tailoring the operating characteristics thereof, said heat-metallization process comprising the steps of forming a thin layer of an active metal over said insulating layer formed over and overlying said intermediate surface portions, and only heating said wafer at a selected temperature between 300* C. and 500* C. which modifies the electrical characteristics of the channel to a desired extent whereby surface trap density along said conduction channel is reduced and the operating characteristics of said transistor are tailored.
Claim 6
Dependent Claim
38 words
The method of claim 7 including the further steps of forming said gate electrode of said active metal prior to subjecting said transistor to said heat-metallization process, and retaining said gate electrode thus formed during said heat-metallization process.
Claim 7
Dependent Claim
35 words
the method of claim 7 wherein said heat-metallization process includes the further step of heating said wafer at said selected temperature for a time at least sufficient to saturate the operating characteristics of said transistor.
Claim 8
Dependent Claim
17 words
The method of claim 7 including the further step of forming said thin metallic layer of aluminum.
Claim 9
Independent Claim
88 words
A method for forming an insulated-gate field effect transistor including the steps of: forming source, drain and gate portions in a semiconductor wafer, forming an insulating layer over at least the surface of said gate portion, forming a thin layer of an active metal on said insulating layer formed over and overlying said surface of said gate portion, and only heating said wafer at a selected temperature while said thin layer of active metal is present on said insulating layer to alter the operating characteristics of said transistor.
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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) | 1974-07-05 | 1975-01-04 | 1975-07-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-07-05 | 1979-01-04 | 1979-07-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-07-05 | 1983-01-04 | 1983-07-06 | $7700.00 | Window Closed / Lapsed |