US5877061A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Methods for roughening and volume expansion of trench sidewalls to form high capacitance trench cell for high density dram applications
Assignee: International Business Machines Corp
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Filing: 1997-02-25
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Granted: 1999-03-02
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Expires: 2017-02-25
Abstract
Abstract Trench cells with increased storage capacity are prepared with roughened sidewalls using a layer of grainy polysilicon or hemispherical grain polysilicon. The top collar region of the trench is protected with oxide while the lower portion of the trench coated with polysilicon or hemispherical grain polysilicon is etched isotropically. The trench structure created has roughened sidewalls for increased volume of storage.
Inventors
- 👤 Scott D. Halle
- 👤 ChorngLii Hwang
- 👤 K. Paul Muller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 02:39
CPC Classifications
H; H10; H10D; H10D1/00; H10D1/60; H10D1/68; H10D1/692; H10D1/711; H10B; H10B12/00; H10B12/01; H10B12/02; H10B12/03; H10B12/038; H10D1/712; Y; Y10; Y10S; Y10S438/00; Y10S438/964
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
103 words
A method of preparing a trench having a roughened surface area comprising the steps of: forming a trench in a substrate through an opening in a dielectric mask material positioned on the substrate; depositing a conformal layer of silicon containing material over said dielectric etch mask material and into said trench; forming a collar oxide in an upper portion of said trench over said conformal layer of silicon containing material, said collar oxide leaving a lower portion of said trench exposed; and isotropically etching said silicon containing material and said substrate under said silicon containing material in said lower portion of said trench.
Claim 2
Independent Claim
103 words
A method of preparing a trench having a roughened surface area comprising the steps of: forming a trench in a substrate through an opening in a dielectric mask material positioned on the substrate; depositing a conformal layer of silicon containing material over said dielectric etch mask material and into said trench; forming a collar oxide in an upper portion of said trench over said conformal layer of silicon containing material, said collar oxide leaving a lower portion of said trench exposed; and isotropically etching said silicon containing material and said substrate under said silicon containing material in said lower portion of said trench.
Claim 3
Dependent Claim
17 words
A method as in claim 1, further comprising depositing node dielectric and polysilicon fill in said trench.
Claim 4
Dependent Claim
17 words
A method as in claim 1, wherein said conformal layer of silicon containing material is amorphous silicon.
Claim 5
Dependent Claim
20 words
A method as in claim 1, wherein said conformal layer of silicon containing material is less than 100 nm thick.
Claim 6
Dependent Claim
16 words
A method as in claim 1 wherein said conformal layer of silicon containing material is polysilicon.
Claim 7
Dependent Claim
11 words
The method of claim 1 wherein said substrate is crystalline silicon.
Claim 8
Independent Claim
77 words
A method of preparing a trench having a roughened surface area comprising the steps of: forming a trench in a substrate through an opening in a dielectric mask material positioned on the substrate; forming a collar oxide in an upper portion of the trench, said collar oxide leaving a lower portion of said trench exposed; depositing a conformal layer of silicon over the dielectric mask material and in the trench; and etching said conformal layer of silicon.
Claim 9
Independent Claim
77 words
A method of preparing a trench having a roughened surface area comprising the steps of: forming a trench in a substrate through an opening in a dielectric mask material positioned on the substrate; forming a collar oxide in an upper portion of the trench, said collar oxide leaving a lower portion of said trench exposed; depositing a conformal layer of silicon over the dielectric mask material and in the trench; and etching said conformal layer of silicon.
Claim 10
Dependent Claim
21 words
A method as in claim 7 further comprising the steps of: depositing a node dielectric; and filling the trench with polysilicon.
Claim 11
Dependent Claim
16 words
A method as in claim 7 wherein said conformal layer of silicon is hemispherical grain polysilicon.
Claim 12
Dependent Claim
14 words
A method as in claim 7 wherein said conformal layer of silicon is polysilicon.
Claim 13
Dependent Claim
17 words
A method as in claim 7 wherein said step of etching is performed by isotropically dry etching.
Claim 14
Dependent Claim
16 words
A method as in claim 11 wherein said step of dry etching is chemical downstream etching.
Claim 15
Dependent Claim
26 words
The method of claim 7 wherein said substrate is crystalline silicon and wherein said step of etching etches said substrate under said conformal layer of silicon.
Claim 16
Dependent Claim
17 words
A method as in claim 7 wherein said step of etching is performed by isotropically wet etching.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2002-03-01 | 2002-08-31 | 2003-03-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-03-01 | 2006-08-31 | 2007-03-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-03-01 | 2010-08-31 | 2011-03-02 | $7700.00 | Window Closed / Lapsed |