US4604789A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for fabricating polysilicon resistor in polycide line
Assignee: Inmos Corp
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Filing: 1985-01-31
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Granted: 1986-08-12
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Expires: 2005-01-31
Abstract
Abstract In making a polysilicon resistor in a polycide line, a thick oxide is established selectively to shield lightly doped polysilicon first from heavy doping and then from the silicide. Before adding silicide, a selected region of polysilicon broader than and including the site of the poly resistor is exposed, lightly doped, and then oxidized to establish a thick oxide, while other areas are protected by nitride. Then the nitride and any thin oxide on top of the polysilicon outside the broad area are removed, and the exposed polysilicon is heavily doped for low resistivity. The thick oxide shields the underlying lightly doped polysilicon from the heavy doping. Silicide is then added. Definition of the polysilicon resistor follows preferably using a two step process. When the silicide is etched, the thick oxide on top of the broad polysilicon area acts as an etch stop. Then the thick oxide and polysilicon resistor are etched.
Inventors
- 👤 Ronald R. Bourassa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 14:00
CPC Classifications
H; H10; H10D; H10D1/00; H10D1/40; H10D1/47; H10P; H10P95/00; H10W; H10W20/00; H10W20/01; H10W20/031; H10W20/064; H10W20/066
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
68 words
A method for fabricating a polysilicon resistor in a polycide line, including the steps of: establishing a protective material on top of a polysilicon region designated for location of the polysilicon resistor before silicide contacts said region; then adding silicide over the polysilicon; and defining the silicide and polysilicon to result in a polysilicon resistor in contact with a polycide line, the resistor being protected from the silicide.
Claim 2
Independent Claim
68 words
A method for fabricating a polysilicon resistor in a polycide line, including the steps of: establishing a protective material on top of a polysilicon region designated for location of the polysilicon resistor before silicide contacts said region; then adding silicide over the polysilicon; and defining the silicide and polysilicon to result in a polysilicon resistor in contact with a polycide line, the resistor being protected from the silicide.
Claim 3
Dependent Claim
31 words
The method of claim 1 wherein said establishing step includes: establishing a layer of polysilicon; doping said designated polysilicon region with impurities for a polysilicon resistor; and establishing said protective material.
Claim 4
Dependent Claim
23 words
The method of claim 2 wherein said establishing said protective material step includes developing an oxide on top of said designated polysilicon region.
Claim 5
Dependent Claim
30 words
The method of claim 3 wherein said step there defined comprises oxidizing said designated polysilicon region, and wherein the method includes establishing an oxidation-inhibiting layer outside said designated polysilicon region.
Claim 6
Dependent Claim
24 words
The method of claim 1 wherein said protective material is established on top of an area larger than and encompassing said designated resistor region.
Claim 7
Dependent Claim
16 words
The method of claim 5 including simultaneously defining both the polycide line and the polysilicon resistor.
Claim 8
Dependent Claim
30 words
The method of claim 6 wherein said method includes establishing photoresist over the silicide and said area encompassing said designated resistor region, and etching silicide, the protective layer, and polysilicon.
Claim 9
Dependent Claim
23 words
The method of claim 5 including defining the polycide line prior to defining the polysilicon into a resistor in the designated resistor region.
Claim 10
Dependent Claim
56 words
The method of claim 8 comprising establishing a photoresist on top of the silicide and in a line extending across said larger area, but being discontinuous over said larger area, then etching through the silicide not covered by said photoresist down to said protective material, and thereafter defining said designated resistor region into the polysilicon resistor.
Claim 11
Dependent Claim
102 words
The method of claim 1 including: covering a layer of polysilicon in which the resistor and polycide lines are to be formed with a layer of oxidation-inhibiting material; etching an opening through said oxidation-inhibiting layer to delineate a region encompassing said designated resistor region; implanting impurities into the polysilicon through said opening; establishing a relatively thick oxide in said opening on top of the polysilicon for preventing subsequently added silicide from contacting the polysilicon in the designated resistor region; adding a layer of silicide covering the polysilicon and said oxide thereon; and defining a polysilicon line passing through the designated resistor area.
Claim 12
Dependent Claim
13 words
The method of claim 10 wherein said oxide is grown in said opening.
Claim 13
Dependent Claim
12 words
The method of claim 10 wherein said oxidation-inhibiting material is a nitride.
Claim 14
Dependent Claim
10 words
The method of claim 12 wherein said oxide is grown.
Claim 15
Dependent Claim
19 words
The method of claim 10 further including removing said oxidation-inhibiting layer prior to said step of adding a silicide.
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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) | 1989-08-11 | 1990-02-10 | 1990-08-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-08-11 | 1994-02-10 | 1994-08-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-08-11 | 1998-02-10 | 1998-08-12 | $7700.00 | Window Closed / Lapsed |