Patent US5789267A successfully refreshed from Google Patents.
US5789267A
Expired / Lapsed
US
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Method of making corrugated cell contact
Assignee: Promos Technologies Inc
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Filing: 1996-08-23
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Granted: 1998-08-04
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Expires: 2016-08-23
Abstract
Abstract A method of forming a cell contact that has improved structural strength and break-down resistance and a cell contact produced by such method are provided. The method utilizes an oxide spacer consisting of a plurality of oxide layers deposited by two alternating methods of thermal CVD and plasma CVD. After a straight contact opening is first etched by a plasma etching technique, the hole is again etched by an etchant such as hydrogen fluoride which has a high selectivity toward oxide layers formed by the plasma CVD method and a low selectivity toward oxide layers formed by the thermal CVD method. As a result, a contact opening having a corrugated side-wall is formed and into which a polysilicon is deposited to substantially fill the hole. A cell contact having a corrugated side-wall configuration is thus formed which presents improved structural rigidity and break-down resistance. A layer of rugged polysilicon layer may optionally be deposited before the deposition of the polysilicon into the contact opening to further increase the surface area of the cell contact.
Inventors
- 👤 Liang-Choo Hsia
- 👤 Thomas Chang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 01:53
CPC Classifications
H; H10; H10B; H10B12/00; H10B12/01; H10B12/02; H10B12/03; H10B12/033; H10B12/30; H10B12/31; H10B12/318; H10D; H10D1/00; H10D1/01; H10D1/041; H10D1/042; H10D1/60; H10D1/68; H10D1/692; H10D1/711; H10D1/714
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
159 words
A method of forming a corrugated cell contact having improved structural rigidity and break-down resistance comprising the steps of: providing a semiconductor substrate, forming an active region in said substrate, depositing a plurality of oxide layers overlying said active region by a deposition method alternating between thermal chemical vapor deposition (CVD) and plasma CVD, etching through said plurality of oxide layers by a first etchant to expose edges of said layers and to expose a contact opening by a first etchant, etching said edges of said plurality of oxide layers in said contact opening by a second etchant having sufficient etch selectivity toward said thermal CVD and said plasma CVD oxide layers such that a corrugated sidewall is formed in said contact opening after said etching step, optionally depositing a layer of rugged polysilicon in said contact opening to substantially cover the surface of said corrugated sidewall, and depositing polysilicon in said contact opening to substantially fill said opening.
Claim 2
Independent Claim
159 words
A method of forming a corrugated cell contact having improved structural rigidity and break-down resistance comprising the steps of: providing a semiconductor substrate, forming an active region in said substrate, depositing a plurality of oxide layers overlying said active region by a deposition method alternating between thermal chemical vapor deposition (CVD) and plasma CVD, etching through said plurality of oxide layers by a first etchant to expose edges of said layers and to expose a contact opening by a first etchant, etching said edges of said plurality of oxide layers in said contact opening by a second etchant having sufficient etch selectivity toward said thermal CVD and said plasma CVD oxide layers such that a corrugated sidewall is formed in said contact opening after said etching step, optionally depositing a layer of rugged polysilicon in said contact opening to substantially cover the surface of said corrugated sidewall, and depositing polysilicon in said contact opening to substantially fill said opening.
Claim 3
Dependent Claim
22 words
A method according to claim 1 further comprising the step of in-situ doping said polysilicon during the filling step by the polysilicon.
Claim 4
Dependent Claim
25 words
A method according to claim 1 further comprising the step of removing said plurality of oxide layers after said contact opening is filled by polysilicon.
Claim 5
Dependent Claim
18 words
A method according to claim 1, wherein said plurality of oxide layers is between 4 and 20 layers.
Claim 6
Dependent Claim
12 words
A method according to claim 1, wherein said second etchant comprises HF.
Claim 7
Dependent Claim
19 words
A method according to claim 1, wherein said etching step by said first etchant is a plasma etching technique.
Claim 8
Dependent Claim
26 words
A method according to claim 1, wherein said sufficient etch selectivity toward said thermal CVD and said plasma CVD oxide layers is at least about 1:2.
Claim 9
Dependent Claim
28 words
A method according to claim 1, wherein said second etchant is HF and said etch toward said thermal CVD and said plasma CVD oxide layers is about 1:4.
Claim 10
Dependent Claim
16 words
A method according to claim 1, wherein said third etchant is similar to said first etchant.
Claim 11
Dependent Claim
33 words
A method according to claim 1, wherein said plurality of oxide layers has a total thickness between about 500 Å and about 5000 Å, preferably between about 1000 Å and about 3000 Å.
Claim 12
Dependent Claim
24 words
A method according to claim 1, wherein said plurality of oxide layers each having a thickness between about 100 Å and about 500 Å.
Claim 13
Independent Claim
146 words
A method of forming a cell contact having improved structural strength comprising the steps of: providing a silicon substrate, forming an active region in the surface of the substrate, blanket depositing a plurality of oxide layers overlying said active region by a deposition method alternating between a thermal CVD and a plasma CVD technique, etching through said plurality of oxide layers to expose a contact opening and edges of said plurality of oxide layers by a plasma etching technique, etching said edges of said plurality of oxide layers in said contact opening by an etchant having sufficient etch selectivity between said thermal CVD and said plasma CVD oxide layers such that a corrugated side-wall is formed in said contact opening after said etching step, deposition polysilicon in said contact opening to substantially fill the opening, and removing said plurality of oxide layers by an etching process.
Claim 14
Independent Claim
146 words
A method of forming a cell contact having improved structural strength comprising the steps of: providing a silicon substrate, forming an active region in the surface of the substrate, blanket depositing a plurality of oxide layers overlying said active region by a deposition method alternating between a thermal CVD and a plasma CVD technique, etching through said plurality of oxide layers to expose a contact opening and edges of said plurality of oxide layers by a plasma etching technique, etching said edges of said plurality of oxide layers in said contact opening by an etchant having sufficient etch selectivity between said thermal CVD and said plasma CVD oxide layers such that a corrugated side-wall is formed in said contact opening after said etching step, deposition polysilicon in said contact opening to substantially fill the opening, and removing said plurality of oxide layers by an etching process.
Claim 15
Dependent Claim
25 words
A method according to claim 12, further comprising the step of depositing a coating having a wave-shape surface prior to the deposition of said polysilicon.
Claim 16
Dependent Claim
28 words
A method according to claim 12 further comprising the step of depositing a rugged polysilicon layer prior to the deposition of said polysilicon to fill the contact opening.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-08-03 | 2002-02-02 | 2002-08-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-08-03 | 2006-02-02 | 2006-08-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-08-03 | 2010-02-02 | 2010-08-04 | $7700.00 | Window Closed / Lapsed |