Patent US4253229A successfully refreshed from Google Patents.
US4253229A
Expired / Lapsed
US
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Self-aligned narrow gate MESFET process
Assignee: Xerox Corp
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Filing: 1978-04-27
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Granted: 1981-03-03
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Expires: 1998-04-27
Abstract
Abstract A method of making a narrow gate MESFET including the steps of placing a layered mask of nitride and polysilicon over a channel region for self-aligning in a substrate, oxidizing and then removing the polysilicon to reduce the remaining polysilicon width, etching the nitride to the polysilicon width, oxidizing the substrate where the nitride defines the gate therein, removing the nitride, and depositing metal on the gate to form the MESFET Schottky gate. Advantages of the improved MESFET include a relatively higher device gain, greater IC density, a self-aligned Schottky gate, controllable minimum series resistance, a relatively short channel using a conventional photo process, and a n- resistor that may be easily simultaneously fabricated therewith.
Inventors
- 👤 Keming Yeh
- 👤 James L. Reuter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:46
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/01; H10D30/061; H10D30/80; H10D30/87; H10D62/00; H10D62/80; H10D62/83
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
138 words
A method of making a narrow gate MESFET comprising the steps of: a. preparing a layered mask of nitride and polysilicon on a substrate over a channel region therein; b. oxidizing a predetermined amount of the polysilicon layer on both sides of said layered mask; c. removing the oxidized polysilicon of said layered mask for allowing the polysilicon layer of said layered mask that remains to be relatively predeterminably narrower than the nitride layer; d. etching the nitride layer of said layered mask to be disposed only under the polysilicon layer of said layered mask thereby defining the gate region; e. oxidizing the surface of the substrate to form an oxide layer of predetermined thickness; f. removing the nitride layer of said layered mask; and g. depositing of metal on the gate region to form the MESFET gate.
Claim 2
Independent Claim
138 words
A method of making a narrow gate MESFET comprising the steps of: a. preparing a layered mask of nitride and polysilicon on a substrate over a channel region therein; b. oxidizing a predetermined amount of the polysilicon layer on both sides of said layered mask; c. removing the oxidized polysilicon of said layered mask for allowing the polysilicon layer of said layered mask that remains to be relatively predeterminably narrower than the nitride layer; d. etching the nitride layer of said layered mask to be disposed only under the polysilicon layer of said layered mask thereby defining the gate region; e. oxidizing the surface of the substrate to form an oxide layer of predetermined thickness; f. removing the nitride layer of said layered mask; and g. depositing of metal on the gate region to form the MESFET gate.
Claim 3
Dependent Claim
47 words
The method of claim 1 wherein said steps of oxidizing a predetermined amount of the polysilicon layer on both sides of said layered mask includes the step of oxidizing the predetermined amount of the polysilicon layer on both sides of said layered mask according to predetermined dimensions.
Claim 4
Dependent Claim
34 words
The method of claim 2 including the step of implanting source and drain regions in said substrate, said source and drain regions are aligned to bound either side of the said defined gate region.
Claim 5
Dependent Claim
62 words
The method of claim 1 wherein said step of preparing said layered mask of nitride and polysilicon includes the step of forming a sandwich of polysilicon between two layers of nitride, and also said step of removing said oxidized layer of polysilicon includes the step of removing the layer of nitride disposed on the opposite side of the polysilicon from the substrate.
Claim 6
Dependent Claim
42 words
The method of claim 3 wherein said step of oxidizing said substrate to define the gate region includes the step of forming oxide over the source and drain regions and removing a portion of said oxide to expose source and drain contacts.
Claim 7
Dependent Claim
23 words
The method of claim 3 wherein said step of implanting source and drain regions includes the step of implanting regions of predetermined dimensions.
Claim 8
Dependent Claim
51 words
The method of claim 5 wherein said step of exposing source and drain regions includes the step of depositing polysilicon over the exposed source and drain regions and also said step of removing said nitride mask precedes the additional step of etching a portion of said oxide to expose polysilicon contacts.
Claim 9
Dependent Claim
21 words
The method of claim 7 wherein said step of depositing includes the step of depositing metal on said exposed polysilicon contacts.
Claim 10
Dependent Claim
42 words
The method of claim 2 wherein said step of oxidizing said substrate to define the gate region includes the step of forming oxide over the source and drain regions and removing a portion of said oxide to expose source and drain contacts.
Claim 11
Dependent Claim
23 words
The method of claim 2 wherein said step of implanting source and drain regions includes the step of implanting regions of predetermined dimensions.
Claim 12
Dependent Claim
52 words
The method of claim 9 wherein said step of exposing source and drain contacts includes the step of depositing polysilicon over the exposed source and drain contacts and also said step of removing said nitride mask precedes the additional step of etching a portion of said oxide to expose a polysilicon contact.
Claim 13
Dependent Claim
21 words
The method of claim 9 wherein said step of depositing includes the step of depositing metal on said exposed polysilicon contacts.
Claim 14
Dependent Claim
58 words
The method of claim 5 wherein said step of exposing source and drain contacts includes the step of depositing polysilicon over one of said exposed contacts, leaving the other said contact exposed and also said step of removing the said nitride mask precedes the additional step of etching a portion of said oxide to expose a polysilicon contact.
Claim 15
Dependent Claim
34 words
The method of claim 13 wherein said step of depositing includes the step of deposition of metal on the exposed polysilicon contact and on said contact remaining reexposed after the deposition of said polysilicon.
Claim 16
Dependent Claim
57 words
The method of claim 9 wherein said step of exposing source and drain contacts includes the step of depositing polysilicon over one of said exposed contacts, leaving the other said contact exposed and also said step of removing said nitride mask precedes the additional step of etching a portion of said oxide to expose a polysilicon contact.
Claim 17
Dependent Claim
35 words
The method of claim 15 wherein said step of depositing includes the step of deposition of metal on the exposed polysilicon contact and on the said contact remaining reexposed after the deposition of said polysilicon.
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) | 1984-03-02 | 1984-09-01 | 1985-03-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-02 | 1988-09-01 | 1989-03-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-02 | 1992-09-01 | 1993-03-03 | $7700.00 | Window Closed / Lapsed |