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US4218267A
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Microelectronic fabrication method minimizing threshold voltage variation
Assignee: Boeing North American Inc
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Filing: 1979-04-23
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Granted: 1980-08-19
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Expires: 1999-04-23
Abstract
Abstract A microelectronic fabrication process for minimizing the threshold voltage variation across the surface of a wafer of semiconductor material. The process precisely specifies the degenerate (or heavily doped) impurity profile distribution by using ion implantation so as to minimize the autodoping of adjacent gate regions immediately after the ion implantation step during gate oxidation, while maximizing the surface concentration of the dopant at the ultimate silicon surface to achieve appropriate surface sheet resistance and junction depth after all circuit fabrication steps have been completed.
Inventors
- 👤 Roy L. Maddox, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 20:54
CPC Classifications
H; H10; H10P; H10P30/00; H10P30/20; H10P30/21; H10B; H10B12/00; H10B12/30; H10D; H10D62/00; H10D62/10; H10D62/17; H10D62/213; H10D62/221; H10D62/235; H10D62/314; H10P30/202; H10P30/204
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
194 words
A method of making a semiconductor circuit having a substantially uniform doping concentration on the surface thereof and a substantially uniform threshold voltage from a body of semiconductor material of a predetermined conductivity type and resistivity, comprising the steps of: defining a pattern on a laterally extending major surface of said body where devices are to be formed; ion implanting locations defined by said pattern on said body a single time with dopant species for forming regions with a predetermined concentration profile of semiconductor material of different resistivity in said body, the maximum concentration of the dopant species lying below said major surface of said body by a predetermined distance and the concentration of the dopant species at the body surface is less than or equal to 10 18 atoms/cm 3 , and subsequently forming devices having substantially the same threshold voltage at said regions during which step said major surface of said body moves with respect to the location of the maximum concentration of the dopant species so that the maximum concentration of the dopant species lies at said major surface of said body at the completion of the step of forming devices.
Claim 2
Independent Claim
194 words
A method of making a semiconductor circuit having a substantially uniform doping concentration on the surface thereof and a substantially uniform threshold voltage from a body of semiconductor material of a predetermined conductivity type and resistivity, comprising the steps of: defining a pattern on a laterally extending major surface of said body where devices are to be formed; ion implanting locations defined by said pattern on said body a single time with dopant species for forming regions with a predetermined concentration profile of semiconductor material of different resistivity in said body, the maximum concentration of the dopant species lying below said major surface of said body by a predetermined distance and the concentration of the dopant species at the body surface is less than or equal to 10 18 atoms/cm 3 , and subsequently forming devices having substantially the same threshold voltage at said regions during which step said major surface of said body moves with respect to the location of the maximum concentration of the dopant species so that the maximum concentration of the dopant species lies at said major surface of said body at the completion of the step of forming devices.
Claim 3
Dependent Claim
23 words
A method as defined in claim 1, wherein said ion implanting step is performed at an energy between 100 keV and 200 KeV.
Claim 4
Dependent Claim
55 words
A method as defined in claim 1, wherein said body is comprised of n-type semiconductor material and said ion implanting step deposits dopant ions such that said regions at semiconductor material are of p+ type, and the maximum concentration of the dopant ions lies below the surface by a distance approximately equal to 4,000 Angstroms.
Claim 5
Dependent Claim
54 words
A method as defined in claim 1, wherein said body is composed of n-type semiconductor material and said ion implanting step deposits dopant ions such that said regions of semiconductor material are of n+ type, and the maximum concentration of dopant ions lies below the surface by a distance approximately equal to 2,500 Angstroms.
Claim 6
Dependent Claim
21 words
A method as defined in claim 1, wherein said step of forming devices comprises forming insulated gate field effect transistor devices.
Claim 7
Dependent Claim
48 words
A method as defined in claim 1, wherein said semiconductor material is silicon, and said step of forming devices comprises the steps of growing a first oxide layer over at least a portion of the semiconductor body; and depositing a first polysilicon layer over said first oxide layer.
Claim 8
Dependent Claim
25 words
A method as defined in claim 3, wherein said dopant ions comprises boron and said maximum concentration is at most 5×10 20 atoms/cm 3 .
Claim 9
Dependent Claim
25 words
A method as defined in claim 4, wherein said dopant ions comprises phosphorous as said maximum concentration is at most 1×10 20 atoms/cm 3 .
Claim 10
Dependent Claim
33 words
A method as defined in claim 6, further comprising the steps of; growing a second oxide layer over said first polysilicon layer; and depositing a second polysilicon layer over said second oxide layer.
References Cited (Backward Citations)
US3895966A
Cited
US3868274A
Cited
US3868274B1
Cited
US4074301A
Cited
US4089712A
Cited
US4052229A
Cited
US4052229B1
Cited
US4128439A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-08-19 | 1984-02-18 | 1984-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-08-19 | 1988-02-18 | 1988-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-08-19 | 1992-02-18 | 1992-08-19 | $7700.00 | Window Closed / Lapsed |