US4305086A
Expired / Lapsed
US
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MNOS Memory device and method of manufacture
Assignee: Intersil Corp
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Filing: 1979-08-27
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Granted: 1981-12-08
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Expires: 1999-08-27
Abstract
Abstract A metal nitride oxide semiconductor (MNOS) memory device having improved memory retention capability is described. Improved memory retention is obtained by ion implanting a non-doping material, such as argon or nitrogen, or a low concentration of an N type dopant, such as phosphorus, into the oxide before depositing the nitride layer. It is believed that the ion implantation results in a nitride-oxide interface conducive to charge storage. The MNOS device produced has a considerably improved memory retention characteristic when compared with an MNOS device which did not have the ion implantation.
Inventors
- 👤 Heshmat Khajezadeh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 07:16
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/60; H10D30/69; H10D64/00; H10D64/01; H10D64/031; H10D64/037
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
146 words
An improved method of forming an MNOS device of the type comprising the steps of: (a) selecting a substrate having a first impurity type; (b) forming a spaced source and drain of opposite conductivity type extending into said substrate from a surface thereof; (c) forming a silicon dioxide layer on the surface of said substrate at least between said source and said drain; (d) forming a silicon nitride layer over the surface of said silicon dioxide layer; and (e) forming a continuous conductive gate over said silicon nitride layer at least overlying a portion of said source and said drain; wherein the improvement comprises implanting ions selected from the group consisting of a non-dopant and a dopant having the same impurity type as said substrate into said silicon dioxide layer, said step of implanting occurring immediately prior to said step of forming a silicon nitride layer.
Claim 2
Dependent Claim
146 words
An improved method of forming an MNOS device of the type comprising the steps of: (a) selecting a substrate having a first impurity type; (b) forming a spaced source and drain of opposite conductivity type extending into said substrate from a surface thereof; (c) forming a silicon dioxide layer on the surface of said substrate at least between said source and said drain; (d) forming a silicon nitride layer over the surface of said silicon dioxide layer; and (e) forming a continuous conductive gate over said silicon nitride layer at least overlying a portion of said source and said drain; wherein the improvement comprises implanting ions selected from the group consisting of a non-dopant and a dopant having the same impurity type as said substrate into said silicon dioxide layer, said step of implanting occurring immediately prior to said step of forming a silicon nitride layer.
Claim 3
Dependent Claim
20 words
The method of claim 1 wherein said substrate has N type conductivity and said implanted ions are ions of phosphorus.
Claim 4
Dependent Claim
19 words
The method of claim 2 wherein said phosphorus ions are implanted at an energy level of about 35 KeV.
Claim 5
Dependent Claim
26 words
The method of claim 3 wherein said ion implantation is continued until there has been a total implantation dose of about 5×10 12 atoms/cm 2 .
Claim 6
Dependent Claim
19 words
The method of claim 1 wherein said non-dopant ions are selected from the group consisting of argon and nitrogen.
Claim 7
Dependent Claim
19 words
The method of claim 5 wherein said ion implantation step is conducted at an energy of about 35 KeV.
Claim 8
Dependent Claim
25 words
The method of claim 6 wherein said ion implantation step is continued until a total dose of about 5×10 12 atoms/cm 2 has been implanted.
Claim 9
Dependent Claim
10 words
The MNOS device formed by the method of claim 1.
Claim 10
Dependent Claim
151 words
An improved MNOS device of the type comprising: (a) a substrate having a first impurity type; (b) a source and a drain spaced from said source, both being of conductivity type opposite to said substrate and extending into said substrate from a surface thereof; (c) a silicon dioxide layer on the surface of said substrate extending at least between said source and said drain, said silicon dioxide layer having a central portion which is substantially thinner than the portions adjacent either said source or said drain; (d) a silicon nitride layer formed on the surface of said silicon dioxide layer; and (e) a continuous conductive gate overlying said silicon nitride layer and at least a portion of said source and said drain; wherein the improvement comprises damage to said silicon dioxide layer at its interface with said silicon nitride layer caused by ion implantation of ions into said silicon dioxide layer.
Claim 11
Dependent Claim
151 words
An improved MNOS device of the type comprising: (a) a substrate having a first impurity type; (b) a source and a drain spaced from said source, both being of conductivity type opposite to said substrate and extending into said substrate from a surface thereof; (c) a silicon dioxide layer on the surface of said substrate extending at least between said source and said drain, said silicon dioxide layer having a central portion which is substantially thinner than the portions adjacent either said source or said drain; (d) a silicon nitride layer formed on the surface of said silicon dioxide layer; and (e) a continuous conductive gate overlying said silicon nitride layer and at least a portion of said source and said drain; wherein the improvement comprises damage to said silicon dioxide layer at its interface with said silicon nitride layer caused by ion implantation of ions into said silicon dioxide layer.
Claim 12
Dependent Claim
12 words
The device of claim 9 wherein said substrate is N type silicon.
Claim 13
Dependent Claim
29 words
The device of claim 10 wherein said damage is caused by ion implanting ions selected from the group consisting of a non-dopant and a dopant having N type impurity.
Claim 14
Dependent Claim
32 words
The device of claim 11 wherein said implanted ions are phosphorus ions implanted at an energy level at about 35 KeV to a total dose of about 5×10 12 atoms/cm 2 .
References Cited (Backward Citations)
US4047974A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-12-07 | 1985-06-08 | 1985-12-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-12-07 | 1989-06-08 | 1989-12-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-12-07 | 1993-06-08 | 1993-12-08 | $7700.00 | Window Closed / Lapsed |