US5679601A
Expired / Lapsed
US
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LOCOS method using encapsulating polysilicon/silicon nitride spacer
Assignee: Hanger Solutions LLC
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Filing: 1996-12-10
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Granted: 1997-10-21
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Expires: 2016-12-10
Abstract
Abstract An improved local oxidation of silicon (LOCOS) method using encapsulating polysilicon/silicon nitride spacer is disclosed. The method includes forming a pad oxide layer on a semiconductor substrate and forming a first silicon nitride layer on the pad oxide layer. The pad oxide layer and the first silicon nitride layer are then patterned and etched by a photoresist mask to define an active region. After removing a portion of the pad oxide layer, an undercut between the first silicon nitride layer and the substrate is formed. A silicon oxide layer is thereafter formed on the substrate, and a polysilicon layer is formed to encapsulate the first silicon nitride layer, the pad oxide layer and the silicon oxide layer. Next, a second silicon nitride layer is formed and etched back to form a silicon nitride spacer on the sidewalls of the polysilicon layer. Using the silicon nitride spacer as a mask, portions of the second silicon nitride layer, the polysilicon layer, the silicon oxide layer and the substrate are etched, and an isolation oxide is finally grown on the substrate using the spacer as a mask.
Inventors
- 👤 Shye-Lin Wu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 03:49
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/60; H10P14/61
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
173 words
A method for forming an isolation region, said method comprising: forming a pad oxide layer on a semiconductor substrate; forming a first silicon nitride layer on the pad oxide layer; patterning and etching the pad oxide layer and the first silicon nitride layer to define an active region by a photoresist mask; removing a portion of the pad oxide layer to form an undercut between the first silicon nitride layer and the substrate; forming a silicon oxide layer on the substrate; forming a polysilicon layer to encapsulate the first silicon nitride layer, the pad oxide layer and the silicon oxide layer; forming a second silicon nitride layer over the polysilicon layer; etching a portion of the second silicon nitride layer to form a silicon nitride spacer on the sidewalls of the polysilicon layer; etching portions of the second silicon nitride layer, the polysilicon layer, the silicon oxide layer and the substrate using said silicon nitride spacer as a mask; and forming an isolation region on the substrate, said spacer serving as a mask.
Claim 2
Independent Claim
173 words
A method for forming an isolation region, said method comprising: forming a pad oxide layer on a semiconductor substrate; forming a first silicon nitride layer on the pad oxide layer; patterning and etching the pad oxide layer and the first silicon nitride layer to define an active region by a photoresist mask; removing a portion of the pad oxide layer to form an undercut between the first silicon nitride layer and the substrate; forming a silicon oxide layer on the substrate; forming a polysilicon layer to encapsulate the first silicon nitride layer, the pad oxide layer and the silicon oxide layer; forming a second silicon nitride layer over the polysilicon layer; etching a portion of the second silicon nitride layer to form a silicon nitride spacer on the sidewalls of the polysilicon layer; etching portions of the second silicon nitride layer, the polysilicon layer, the silicon oxide layer and the substrate using said silicon nitride spacer as a mask; and forming an isolation region on the substrate, said spacer serving as a mask.
Claim 3
Dependent Claim
22 words
The method according to claim 1, wherein the thickness of the removed portion of the substrate is between 0 and 2000 angstroms.
Claim 4
Dependent Claim
19 words
The method according to claim 1, wherein the lateral depth of the undercut is between 0 and 1000 angstroms.
Claim 5
Dependent Claim
21 words
The method according to claim 1, wherein said portion of the substrate is etched using a reactive ion etch (RIE) method.
Claim 6
Dependent Claim
19 words
The method according to claim 1, wherein said portion of the substrate is etched using a plasma etch method.
Claim 7
Dependent Claim
24 words
The method according to claim 1, wherein said undercut is formed using a wet etch, a diluted hydrofluoric (HF) solution serving as an etchant.
Claim 8
Dependent Claim
24 words
The method according to claim 1, wherein said undercut is formed using a wet etch, a buffered oxide etch (BOE) serving as an etchant.
Claim 9
Independent Claim
159 words
A method for forming an isolation region, said method comprising: forming a pad oxide layer on a semiconductor substrate; forming a first silicon nitride layer on the pad oxide layer; pattenting and etching the pad oxide layer and the first silicon nitride layer to define an active region by a photoresist mask; removing a portion of the pad oxide layer to form an undercut between the first silicon nitride layer and the substrate; forming a polysilicon layer to encapsulate the first silicon nitride layer, the pad oxide layer and the substrate; forming a second silicon nitride layer over the polysilicon layer; etching a portion of the second silicon nitride layer to form a silicon nitride spacer on the sidewalls of the polysilicon layer; etching portions of the second silicon nitride layer, the polysilicon layer and the substrate using said silicon nitride spacer as a mask; and forming an isolation region on the substrate, said spacer serving as a mask.
Claim 10
Independent Claim
159 words
A method for forming an isolation region, said method comprising: forming a pad oxide layer on a semiconductor substrate; forming a first silicon nitride layer on the pad oxide layer; pattenting and etching the pad oxide layer and the first silicon nitride layer to define an active region by a photoresist mask; removing a portion of the pad oxide layer to form an undercut between the first silicon nitride layer and the substrate; forming a polysilicon layer to encapsulate the first silicon nitride layer, the pad oxide layer and the substrate; forming a second silicon nitride layer over the polysilicon layer; etching a portion of the second silicon nitride layer to form a silicon nitride spacer on the sidewalls of the polysilicon layer; etching portions of the second silicon nitride layer, the polysilicon layer and the substrate using said silicon nitride spacer as a mask; and forming an isolation region on the substrate, said spacer serving as a mask.
Claim 11
Dependent Claim
22 words
The method according to claim 8, wherein the thickness of the removed portion of the substrate is between 0 and 2000 angstroms.
Claim 12
Dependent Claim
19 words
The method according to claim 8, wherein the lateral depth of the undercut is between 0 and 1000 angstroms.
Claim 13
Dependent Claim
21 words
The method according to claim 8, wherein said portion of the substrate is etched using a reactive ion etch (RIE) method.
Claim 14
Dependent Claim
19 words
The method according to claim 8, wherein said portion of the substrate is etched using a plasma etch method.
Claim 15
Dependent Claim
24 words
The method according to claim 8, wherein said undercut is formed using a wet etch, a diluted hydrofluoric (HF) solution serving as an etchant.
Claim 16
Dependent Claim
24 words
The method according to claim 8, wherein said undercut is formed using a wet etch, a buffered oxide etch (BOE) serving as an etchant.
Claim 17
Independent Claim
171 words
A method for forming an isolation region, said method comprising: forming a pad oxide layer on a semiconductor substrate; forming a first silicon nitride layer on the pad oxide layer; patterning and etching the pad oxide layer and the first silicon nitride layer to define an active region by a photoresist mask; removing a portion of the pad oxide layer to form an undercut between the first silicon nitride layer and the substrate; forming a silicon oxide layer on the substrate; forming a polysilicon layer to encapsulate the first silicon nitride layer, the pad oxide layer and the silicon oxide layer; forming a second silicon nitride layer over the polysilicon layer; etching a portion of the second silicon nitride layer to form a silicon nitride spacer on the sidewalls of the polysilicon layer; etching portions of the second silicon nitride layer, the polysilicon layer and the silicon oxide layer using said silicon nitride spacer as a mask; and forming an isolation region on the substrate, said spacer serving as a mask.
Claim 18
Independent Claim
171 words
A method for forming an isolation region, said method comprising: forming a pad oxide layer on a semiconductor substrate; forming a first silicon nitride layer on the pad oxide layer; patterning and etching the pad oxide layer and the first silicon nitride layer to define an active region by a photoresist mask; removing a portion of the pad oxide layer to form an undercut between the first silicon nitride layer and the substrate; forming a silicon oxide layer on the substrate; forming a polysilicon layer to encapsulate the first silicon nitride layer, the pad oxide layer and the silicon oxide layer; forming a second silicon nitride layer over the polysilicon layer; etching a portion of the second silicon nitride layer to form a silicon nitride spacer on the sidewalls of the polysilicon layer; etching portions of the second silicon nitride layer, the polysilicon layer and the silicon oxide layer using said silicon nitride spacer as a mask; and forming an isolation region on the substrate, said spacer serving as a mask.
Claim 19
Dependent Claim
19 words
The method according to claim 15, wherein the lateral depth of the undercut is between 0 and 1000 angstroms.
Claim 20
Dependent Claim
24 words
The method according to claim 15, wherein said undercut is formed using a wet etch, a diluted hydrofluoric (HF) solution serving as an etchant.
Claim 21
Dependent Claim
24 words
The method according to claim 15, wherein said undercut is formed using a wet etching, a buffered oxide etch (BOE) serving as an etchant.
References Cited (Backward Citations)
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