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US5650344A
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Method of making non-uniformly nitrided gate oxide
Assignee: Intersil Americas LLC
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Filing: 1995-07-17
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Granted: 1997-07-22
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Expires: 2015-07-17
Abstract
Abstract A method of making a semiconductor device in which a polysilicon gate is separated from a semiconductor substrate by a re-oxidized nitrided oxide film and in which the concentration of re-oxidized nitride in the film underlying the gate is non-uniform. The concentration of nitrogen in the substrate and the re-oxidized nitrided oxide along their interface and underlying the gate is non-uniform. The non-uniform concentrations are provided by incomplete shielding of the oxide by the gate during the nitriding and re-oxidizing processes.
Inventors
- 👤 Akira Ito
- 👤 John T. Gasner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 03:25
CPC Classifications
H; H10; H10D; H10D64/00; H10D64/01; H10D64/013; H10D64/01302; H10D64/01332; H10D64/01336; H10D64/01346; H10D30/00; H10D30/01; H10D30/021; H10D30/0223; H10D64/01338; H10D64/60; H10D64/66; H10D64/68; H10D64/693; Y; Y10; Y10S; Y10S148/00; Y10S148/043; Y10S148/044; Y10S148/112; Y10S148/114; Y10S438/00; Y10S438/954
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
155 words
A method of forming a gate oxide having a non-uniform concentration of re-oxidized nitrided oxide for a semiconductor device comprising the steps of: a) forming an oxide film on the upper surface of a semiconductor substrate; b) forming a polysilicon layer on the oxide film; c) selectively removing the polysilicon layer to define a polysilicon gate with the oxide film underlying the polysilicon gate defining a gate oxide; d) exposing the oxide film to a nitrogen containing ambient to thereby nitride the oxide film and to form a region of non-zero nitrogen concentration along an interface of the semiconductor substrate and the oxide film; and e) exposing the nitrided oxide film to a dry oxygen ambient to thereby form a re-oxidized nitrided oxide film in which a concentration of re-oxidized nitrided oxide is non-zero, and in which the re-oxidized nitrided oxide film and the region of non-zero nitrogen concentration underlie the entirety of the gate.
Claim 2
Independent Claim
155 words
A method of forming a gate oxide having a non-uniform concentration of re-oxidized nitrided oxide for a semiconductor device comprising the steps of: a) forming an oxide film on the upper surface of a semiconductor substrate; b) forming a polysilicon layer on the oxide film; c) selectively removing the polysilicon layer to define a polysilicon gate with the oxide film underlying the polysilicon gate defining a gate oxide; d) exposing the oxide film to a nitrogen containing ambient to thereby nitride the oxide film and to form a region of non-zero nitrogen concentration along an interface of the semiconductor substrate and the oxide film; and e) exposing the nitrided oxide film to a dry oxygen ambient to thereby form a re-oxidized nitrided oxide film in which a concentration of re-oxidized nitrided oxide is non-zero, and in which the re-oxidized nitrided oxide film and the region of non-zero nitrogen concentration underlie the entirety of the gate.
Claim 3
Dependent Claim
26 words
The method of claim 1 wherein the concentration of re-oxidized nitrided oxide in a center of the gate oxide is less than in a periphery thereof.
Claim 4
Dependent Claim
31 words
The method of claim 1 further comprising the additional step of forming a second oxide film overlying the oxide film and polysilicon gate without increasing the thickness of the gate oxide.
Claim 5
Dependent Claim
31 words
The method of claim 1 further comprising the additional step of forming source and drain regions in the semiconductor substrate prior to exposing the oxide film to the nitrogen containing ambient.
Claim 6
Dependent Claim
22 words
The method of claim 1 wherein the concentration of nitrogen in the portion of the nitrogen region underlying the gate is non-uniform.
Claim 7
Dependent Claim
32 words
The method of claim 5 wherein the concentration of nitrogen in the portion of the nitrogen region underlying the gate is between about 0.1% and 20.0% by atomic weight along the interface.
Claim 8
Dependent Claim
52 words
The method of claim 5 wherein the concentration of nitrogen in the portion of the nitrogen region underlying the gate is greater than zero and less than about 4% by atomic weight under a center of the gate and greater than about 10% by atomic weight under a periphery of the gate.
Claim 9
Dependent Claim
34 words
The method of claim 1 wherein the exposure of the oxide film to the nitrogen containing ambient is between about 1 and 180 seconds at a temperature between about 900° C. and 1200° C.
Claim 10
Dependent Claim
35 words
The method of claim 1 wherein the exposure of the nitrided oxide film to the dry oxygen ambient is between about 10 and 180 seconds at a temperature between about 900° C. and 1200° C.
Claim 11
Dependent Claim
14 words
The method of claim 1 wherein the nitrogen containing ambient contains NH 3 .
Claim 12
Dependent Claim
14 words
The method of claim 1 wherein the nitrogen containing ambient contains N 2 O.
Claim 13
Dependent Claim
79 words
In a method of forming a re-oxidized nitrided oxide region in a semiconductor device having an oxide film formed on a semiconductor substrate and a polysilicon gate formed on the oxide film, the improvement comprising forming the polysilicon gate on the oxide film prior to nitriding and re-oxidizing the oxide film and nitriding and re-oxidizing the oxide film so that the re-oxidized nitrided oxide region extends completely under the gate and has a non-zero concentration of re-oxidized nitrided oxide.
Claim 14
Dependent Claim
79 words
In a method of forming a re-oxidized nitrided oxide region in a semiconductor device having an oxide film formed on a semiconductor substrate and a polysilicon gate formed on the oxide film, the improvement comprising forming the polysilicon gate on the oxide film prior to nitriding and re-oxidizing the oxide film and nitriding and re-oxidizing the oxide film so that the re-oxidized nitrided oxide region extends completely under the gate and has a non-zero concentration of re-oxidized nitrided oxide.
Claim 15
Dependent Claim
33 words
The method of claim 12 wherein the nitriding of the oxide film forms a nitrogen region in the semiconductor substrate with the concentration of nitrogen in the region underlying the gate being non-uniform.
Claim 16
Dependent Claim
28 words
The method of claim 13 wherein the concentration of nitrogen in the region underlying a center of the gate is no greater than about 4% by atomic weight.
Claim 17
Dependent Claim
25 words
The method of claim 13 wherein the concentration of nitrogen in the region underlying the gate is between about 4% and 10% by atomic weight.
Claim 18
Dependent Claim
23 words
The method of claim 13 wherein the concentration of nitrogen in the region is at a minimum underneath the center of the gate.
Claim 19
Independent Claim
242 words
A method, in a semiconductor device having an oxide film formed on a semiconductor substrate and a polysilicon gate formed on the oxide film, of (i) forming a gate oxide having a non-uniform concentration of re-oxidized nitrided oxide within said oxide film, and (ii) forming a nitrogen region along an interface of the oxide film and substrate having a non-uniform concentration of nitrogen under the gate oxide, the method comprising the steps of: a) forming an oxide film on an upper surface of a semiconductor substrate; b) forming a polysilicon layer on the oxide film; c) selectively removing the polysilicon layer to define a polysilicon gate having a width with the oxide film under the polysilicon gate defining a gate oxide; d) exposing the oxide film and polysilicon gate for between about 1 and 180 seconds to a nitrogen containing ambient having a temperature between about 900° C. and 1200° C., the polysilicon gate partially shielding the gate oxide from exposure to the nitrogen containing ambient and thereby non-uniformly nitriding the gate oxide over the width thereof and forming a nitrogen region having a non-uniform concentration of nitrogen under the gate oxide; and e) exposing the oxide film for between about 10 and 180 seconds to a dry oxygen ambient having a temperature between about 900° C. and 1200° C., thereby forming a gate oxide having a non-uniform and non-zero concentration of re-oxidized nitrided oxide over an entirety of the width thereof.
Claim 20
Independent Claim
242 words
A method, in a semiconductor device having an oxide film formed on a semiconductor substrate and a polysilicon gate formed on the oxide film, of (i) forming a gate oxide having a non-uniform concentration of re-oxidized nitrided oxide within said oxide film, and (ii) forming a nitrogen region along an interface of the oxide film and substrate having a non-uniform concentration of nitrogen under the gate oxide, the method comprising the steps of: a) forming an oxide film on an upper surface of a semiconductor substrate; b) forming a polysilicon layer on the oxide film; c) selectively removing the polysilicon layer to define a polysilicon gate having a width with the oxide film under the polysilicon gate defining a gate oxide; d) exposing the oxide film and polysilicon gate for between about 1 and 180 seconds to a nitrogen containing ambient having a temperature between about 900° C. and 1200° C., the polysilicon gate partially shielding the gate oxide from exposure to the nitrogen containing ambient and thereby non-uniformly nitriding the gate oxide over the width thereof and forming a nitrogen region having a non-uniform concentration of nitrogen under the gate oxide; and e) exposing the oxide film for between about 10 and 180 seconds to a dry oxygen ambient having a temperature between about 900° C. and 1200° C., thereby forming a gate oxide having a non-uniform and non-zero concentration of re-oxidized nitrided oxide over an entirety of the width thereof.
Claim 21
Independent Claim
57 words
A method of providing a non-uniform concentration of nitrogen in a semiconductor substrate underlying a gate oxide comprising the step of incompletely shielding the gate oxide with a gate prior to nitriding the gate oxide and nitriding the gate oxide so that the non-uniform concentration of nitrogen is greater than zero and extends completely under the gate.
Claim 22
Independent Claim
57 words
A method of providing a non-uniform concentration of nitrogen in a semiconductor substrate underlying a gate oxide comprising the step of incompletely shielding the gate oxide with a gate prior to nitriding the gate oxide and nitriding the gate oxide so that the non-uniform concentration of nitrogen is greater than zero and extends completely under the gate.
Claim 23
Independent Claim
64 words
A method of providing a non-uniform boron diffusion barrier between a boron doped polysilicon gate and an underlying semiconductor substrate comprising the step of incompletely shielding a gate oxide between the polysilicon gate and the substrate prior to nitriding the gate oxide and nitriding the gate oxide so that the non-uniform concentration of nitrogen is greater than zero and extends completely under the gate.
Claim 24
Independent Claim
64 words
A method of providing a non-uniform boron diffusion barrier between a boron doped polysilicon gate and an underlying semiconductor substrate comprising the step of incompletely shielding a gate oxide between the polysilicon gate and the substrate prior to nitriding the gate oxide and nitriding the gate oxide so that the non-uniform concentration of nitrogen is greater than zero and extends completely under the gate.
References Cited (Backward Citations)
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