Patent US348437A successfully refreshed from Google Patents.
US5482883A
Expired / Lapsed
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Method for fabricating low leakage substrate plate trench DRAM cells and devices formed thereby
Assignee: International Business Machines Corp
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Filing: 1994-11-10
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Granted: 1996-01-09
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Expires: 2014-11-10
Abstract
Abstract Methods for fabricating low leakage trenches for Dynamic Random Access Memory (DRAM) cells and the devices formed thereby are disclosed. In one embodiment of the present invention, the method includes forming a diffusion ring surrounding an upper portion of the trench. In another embodiment, a portion of the diffusion ring extends to the surface of a substrate. The diffusion ring can be formed by outdiffusing a dopant from a doped material deposited within the trench. In a further embodiment, the present method includes forming an insulating ring surrounding an upper portion of the trench. The insulating ring can be formed by thermal oxidation or by etching a sidewall shallow trench and depositing an insulating material therein. In another embodiment, a portion of the insulating ring extends to the surface of the substrate.
Inventors
- 👤 Thekkemadathil V. Rajeevakumar
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 16:59
CPC Classifications
H; H10; H10B; H10B12/00; H10B12/30; H10B12/37
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
177 words
A method for forming a diffusion ring around a trench of a DRAM cell comprising the steps of: (a) providing a substrate having a lightly doped upper portion of one conductivity type overlying a heavily doped lower portion of the same conductivity type; (b) forming a protective layer on a surface of said substrate; (c) etching a trench to a first depth into said upper portion of said substrate at a first region; (d) forming a nitride collar on the sidewall surfaces of said trench; (e) etching said trench to a second depth beyond said nitride collar and within said upper portion of said substrate; (f) forming a diffusion ring of the second conductivity type extending from said nitride collar and within said upper portion of said substrate; and (g) etching said trench to a third depth beyond the upper portion and within the lower portion of the substrate such that said diffusion ring surrounds an upper portion of said trench, said diffusion ring being contiguous with said trench on all sides and not within said trench.
Claim 2
Independent Claim
177 words
A method for forming a diffusion ring around a trench of a DRAM cell comprising the steps of: (a) providing a substrate having a lightly doped upper portion of one conductivity type overlying a heavily doped lower portion of the same conductivity type; (b) forming a protective layer on a surface of said substrate; (c) etching a trench to a first depth into said upper portion of said substrate at a first region; (d) forming a nitride collar on the sidewall surfaces of said trench; (e) etching said trench to a second depth beyond said nitride collar and within said upper portion of said substrate; (f) forming a diffusion ring of the second conductivity type extending from said nitride collar and within said upper portion of said substrate; and (g) etching said trench to a third depth beyond the upper portion and within the lower portion of the substrate such that said diffusion ring surrounds an upper portion of said trench, said diffusion ring being contiguous with said trench on all sides and not within said trench.
Claim 3
Dependent Claim
65 words
The method of claim 1, wherein said step of forming said diffusion ring comprises: depositing a doped material having a dopant of the second conductivity type on all surfaces of said trench; outdiffusing said dopant into said upper portion of said substrate to form said diffusion ring; and removing said doped material from said nitride collar and all vertical and horizontal surfaces of said trench.
Claim 4
Dependent Claim
40 words
The method of claim 2, wherein said doped material is a material selected from the group consisting of arsenic doped glass, phosphorous doped glass, and antimony doped glass, and said first and second conductivity types are p-type and n-type respectively.
Claim 5
Dependent Claim
37 words
The method of claim 2, wherein said doped material is a material selected from the group consisting of boron doped glass, and indium doped glass, and said first and second conductivity types are n-type and p-type respectively.
Claim 6
Dependent Claim
23 words
The method of claim 2, wherein said out diffusing step comprises heating the structure to drive the dopant into the substrate trench sidewalls.
Claim 7
Dependent Claim
40 words
The method of claim 5, wherein said out diffusing step comprises heating the structure to a temperature between 900° C. and 1200° C. for a period of one to six hours to drive the dopant into the substrate trench sidewalls.
Claim 8
Dependent Claim
46 words
The method of claim 1, wherein said step of forming said nitride collar further includes the step of removing a portion of said nitride collar from a sidewall of said trench such that a portion of said diffusion ring extends to a surface of said substrate.
Claim 9
Dependent Claim
46 words
The method of claim 7, wherein said step of removing a portion of said nitride collar includes the steps of: depositing a planarization resist within said trench; masking a portion of said filled trench; removing a portion of said nitride collar; and removing said planarization resist.
Claim 10
Dependent Claim
48 words
The method of claim 1, further including the step of forming a region of a second conductivity type in said upper portion of said substrate, said region extending from the surface of said substrate and beyond the diffusion ring, said diffusion ring being disposed entirely within said region.
Claim 11
Dependent Claim
33 words
The method of claim 1, wherein said step of forming said protective layer comprises: depositing a nitride layer on the surface of said substrate; and depositing an oxide layer on said nitride layer.
Claim 12
Dependent Claim
49 words
The method of claim 1, wherein said step of forming the nitride collar comprises: depositing a nitride layer on all surfaces of said trench; etching the nitride collar formed on the horizontal surface of the trench to leave the nitride collar on all vertical sidewall surfaces of the trench.
Claim 13
Independent Claim
159 words
A method of forming an insulating ring around a trench of a DRAM cell comprising the steps of: (a) providing a substrate having a lightly doped upper portion of one conductivity type overlying a heavily doped lower portion of the same conductivity type: (b) forming a protective layer on a surface of said upper portion of the substrate; (c) etching a trench to a first depth into said upper portion of said substrate at a first region; (d) forming an oxide layer on all surface of said trench below said substrate surface; and (e) selectively exposing an annular portion of said upper portion of said substrate by removing a portion of said oxide layer and forming an insulating ring within said exposed annular portion of said upper portion of said substrate, spaced from said substrate surface and surrounding a portion of the trench, said insulating ring being continuous with said trench on all sides and not within said trench.
Claim 14
Independent Claim
159 words
A method of forming an insulating ring around a trench of a DRAM cell comprising the steps of: (a) providing a substrate having a lightly doped upper portion of one conductivity type overlying a heavily doped lower portion of the same conductivity type: (b) forming a protective layer on a surface of said upper portion of the substrate; (c) etching a trench to a first depth into said upper portion of said substrate at a first region; (d) forming an oxide layer on all surface of said trench below said substrate surface; and (e) selectively exposing an annular portion of said upper portion of said substrate by removing a portion of said oxide layer and forming an insulating ring within said exposed annular portion of said upper portion of said substrate, spaced from said substrate surface and surrounding a portion of the trench, said insulating ring being continuous with said trench on all sides and not within said trench.
Claim 15
Dependent Claim
50 words
The method of claim 12, further including the step of forming a region of a second conductivity type in said lightly doped upper portion of said substrate, said region extending from the surface of said substrate and beyond the insulating ring, said insulating ring being disposed entirely within said region.
Claim 16
Dependent Claim
44 words
The method of claim 12, wherein said step of forming said protective layer comprises: depositing a first nitride layer on the surface of said substrate; depositing an oxide layer on said first nitride layer; and depositing a second nitride layer on said oxide layer.
Claim 17
Dependent Claim
93 words
The method of claim 12 wherein said trench comprises first, second and third contiguous regions, said first region being a horizontal surface and lower vertical surface of said trench, said third region being vertical surfaces of an uppermost portion of the trench and said second region being vertical surfaces of said trench between said first and third regions, said insulating ring being formed at said second region of said trench, said insulating ring forming step further including forming a nitride layer on first and third regions of said trench over said oxide layer.
Claim 18
Dependent Claim
97 words
The method of claim 15, wherein said step of forming said nitride layer comprises: depositing a nitride layer within said trench over said oxide layer; forming a planarization resist within said trench on said nitride layer and recessing said resist to leave said resist within said first trench region; etching said nitride layer to leave a nitride layer only on said first trench region; depositing polysilicon in said first and second trench regions; forming a nitride collar on said third trench region; and isotropically etching said polysilicon while leaving said nitride layer on said third trench region.
Claim 19
Dependent Claim
40 words
The method of claim 15, wherein said step of forming the insulating ring comprises: growing said oxide layer on said second region subsequent to the exposure thereof; and anisotropically etching any of said nitride layer that is within said trench.
Claim 20
Dependent Claim
16 words
The method of claim 17, wherein said growing step is performed in an atmosphere of nitride.
Claim 21
Dependent Claim
15 words
The method of claim 17, wherein said growing step is performed in an ammonia atmosphere.
Claim 22
Dependent Claim
29 words
The method of claim 15, further including the step of anisotropically etching said nitride layer to remove the nitride layer from the first and third regions of said trench.
Claim 23
Dependent Claim
54 words
The method of claim 20, further including the step of: etching said trench to a second depth within said heavily doped lower portion of said substrate such that said insulating ring surrounds an upper portion of said trench, said insulating ring being contiguous with said trench on all sides and not within said trench.
Claim 24
Dependent Claim
56 words
The method of claim 15, wherein said step of forming a nitride layer further comprises removing said nitride layer from one vertical surface of said third trench region such that during said step of forming the insulating ring a portion of said insulating ring at said one vertical surface extends to the surface of said substrate.
Claim 25
Dependent Claim
58 words
The method of claim 22, wherein said step of removing said nitride layer comprises: forming a planarization resist within said trench to a level substantially equal to that of the surface of said protective layer; forming a mask on said surface having an opening; removing said nitride layer from said one vertical surface; and removing said planarization resist.
Claim 26
Dependent Claim
69 words
The method of claim 12, wherein said step of forming the insulating ring comprises: isotropically etching said portion of said trench to form a shallow annular recessed region in the sidewall of said trench; depositing an insulating material within said trench and said shallow annular recessed region; and etching said insulating material within said trench to leave a portion of said insulating material within said shallow annular recessed region.
References Cited (Backward Citations)
US4830981A
Cited
US4784969A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-01-08 | 1999-07-10 | 2000-01-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-01-08 | 2003-07-10 | 2004-01-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-01-08 | 2007-07-10 | 2008-01-09 | $7700.00 | Window Closed / Lapsed |