EP0641022A2
Expired / Lapsed
EP
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Isolation structure and method for making same
Assignee: STMicroelectronics lnc USA
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Filing: 1994-08-26
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Granted: —
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Expires: 2014-08-26
Abstract
Abstract A method for creating isolation structures in a substrate without having to increase the field implant doses to prevent punch through. This particular advantage is achieved by first growing a pad oxide on the substrate. Polysilicon is deposited on top of the pad oxide layer. Next, silicon nitride, used for masking, is deposited on the polysilicon layer. An opening, also called an isolation space, is etched into the three layers, exposing part of the substrate. A first field oxide is grown in the opening. This first field oxide layer is etched to expose a portions of the substrate along the edge of the field oxide region. Then, trenches are etched into the exposed portions of the substrate, and field implantation of dopants is performed. After implantation, a second field oxide layer is grown. The silicon nitride, polysilicon, and pad oxide are then removed, resulting in the isolation structure of the present invention.
Inventors
- 👤 Tsui Chiu Chan
- 👤 Frank Randolph Bryant
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 15:10
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/60; H10P14/61; H10W; H10W10/00; H10W10/01; H10W10/011; H10W10/012; H10W10/0128; H10W10/10; H10W10/13
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
87 words
A method for creating an isolation structure in a substrate comprising: forming an oxidation barrier over a substrate; forming an opening in the oxidation barrier to define a field oxide region; oxidizing the substrate in the field oxide region to form a field oxide layer; removing part of the field oxide layer to expose a portion of the substrate; forming a trench in the exposed portion of the substrate; and oxidizing the exposed portion of the substrate to form a second field oxide region filling the trench.
Claim 2
Dependent Claim
33 words
The method of claim 1 further comprising implanting a dopant in the trench prior to the step of oxidizing the exposed portion of the substrate to form a field oxide in the trench.
Claim 3
Dependent Claim
58 words
The method of claim 1, wherein the step of oxidizing the exposed portion of the substrate to form a field oxide in the trench comprises: depositing polysilicon, wherein the trench is filled with polysilicon; etching away polysilicon from the nitride layer; and oxidizing a top portion of the polysilicon to form a field oxide that fills the trench.
Claim 4
Dependent Claim
39 words
The method of claim 1, wherein the oxidation barrier is formed by: growing a pad oxide layer on the substrate; depositing a polysilicon layer on the pad oxide layer; and depositing a silicon nitride layer on the polysilicon layer.
Claim 5
Dependent Claim
21 words
The method of claim 1, wherein the step of forming and opening comprises etching the oxidation barrier with an anisotropic etch.
Claim 6
Dependent Claim
45 words
The method of claim 1, wherein the step of removing part of the field oxide layer comprises one of: etching the field oxide layer with an isotropic etch; wet isotropic etching of the field oxide layer; or etching the field oxide layer with hydrogen fluoride.
Claim 7
Dependent Claim
30 words
The method of claim 1, wherein the step of forming a trench comprises etching the exposed portion of substrate with either an anisotropic etch or with a dry anisotropic etch.
Claim 8
Independent Claim
95 words
A method for creating an isolation structure in a substrate comprising: growing a pad oxide layer on the substrate; depositing a first polysilicon layer; depositing a silicon nitride layer; creating an isolation space exposing a section of the substrate; growing a first field oxide layer on the exposed substrate; etching the first field oxide layer to expose a preselected amount of substrate; etching at least one trench in the exposed substrate; growing a second field oxide layer, wherein the at least one trench is filled; and removing the silicon nitride, polysilicon, and pad oxide layers.
Claim 9
Dependent Claim
35 words
The method of claim 8, wherein the step of creating an isolation space includes etching the silicon nitride layer, the first polysilicon layer, and the pad oxide layer away from a portion of the substrate.
Claim 10
Dependent Claim
48 words
The method of claim 9, wherein the step of etching the first field oxide layer includes one of: isotropic etching of the first field oxide layer; wet isotropic etching of the first field oxide layer; or wet isotropic etching of the first field oxide layer with hydrogen fluoride.
Claim 11
Dependent Claim
22 words
The method of claim 9, wherein the step of etching at least one trench includes either anisotropic etching or dry anisotropic etching.
Claim 12
Dependent Claim
27 words
The method of claim 9, further comprising implanting a dopant in the at least one trench prior to the step of growing a second field oxide layer.
Claim 13
Independent Claim
185 words
A method for creating an isolation structure in a substrate comprising: growing a pad oxide layer from about 25 Å to about 150 Å thick on the substrate: depositing a first polysilicon layer from about 50 Å to about 500 Å thick on the pad oxide layer; depositing a silicon nitride layer from about 500 Å to about 2500 Å thick on the first polysilicon layer; creating an isolation space in the pad oxide, first polysilicon, and silicon nitride layers to expose a section of substrate; growing a first field oxide layer from about 500 Å to about 4000 Å thick on the exposed substrate; etching away about 500 Å to about 3000 Å of the first field oxide layer to expose a preselected area of substrate; etching at least one trench in the exposed substrate; implanting a dopant in the at least one trench; growing a second field oxide layer, wherein the at least one trench is filled and the field oxide layer is about 1000 Å to about 4000 Å above the substrate; and removing the silicon nitride, polysilicon, and pad oxide layers.
Claim 14
Independent Claim
207 words
A method for creating an isolation structure in a substrate comprising: growing a pad oxide layer from about 25 Å to about 150 Å thick on the substrate; depositing a first polysilicon layer from about 50 Å to about 500 Å thick on the pad oxide layer; depositing a silicon nitride layer from about 500 Å to about 2500 Å thick on the first polysilicon layer; creating an isolation space in the pad oxide, first polysilicon, and nitride layers to expose a section of substrate; growing a first field oxide layer from about 500 Å to about 3000 Å thick on the exposed section of substrate; etching away about 500 Å to about 3000 Å of the first field oxide layer to expose a preselected area of substrate; etching at least one trench in the exposed substrate; growing a thin oxide from about 50 Å to about 1000 Å; implanting a dopant in the at least one trench; depositing polysilicon, wherein the at least one trench is filled with polysilicon; etching away polysilicon from the nitride layer; oxidizing a top portion of the polysilicon to form a poly filled trench in the at least one trench; and removing the silicon nitride, first polysilicon, and pad oxide layers.
References Cited (Backward Citations)
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