US6339015B1
Expired / Lapsed
US
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Method of fabricating a non-volatile semiconductor device
Assignee: International Business Machines Corp
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Filing: 2000-05-18
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Granted: 2002-01-15
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Expires: 2020-05-18
Abstract
Abstract A non-volatile random access memory (NVRAM) cell and methods of forming thereof are disclosed. The NVRAM cell includes a substrate having source and drain regions. A spike having a sharp tip extends in the source region. Instead of a single spike, two adjacent spikes are included in the source. Alternatively, in addition to the single spike in the source, two adjacent spikes are included in the drain. The two adjacent spikes have one tip pointing toward the floating gate and two tips pointing away from the floating gate. The spikes provide high electric field to facilitate charge movement between the floating gate and the source region. A tunnel oxide layer separates the floating gate from the substrate. A gate oxide and a control gate are also formed over the floating gate. The single spike is formed by preferentially etching the substrate along a selected crystal plane through an opening formed in a mask that covers the substrate. The two adjacent spikes are formed by first forming spacers on sidewalls of the opening to reduce a width thereof; filling the reduced opening with a mask plug; removing the sidewalls; and etching the substrate.
Inventors
- 👤 John A. Bracchitta
- 👤 James S. Nakos
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 15:40
CPC Classifications
H; H10; H10B; H10B69/00; H10D; H10D30/00; H10D30/60; H10D30/68; H10D30/681; H10D30/683; H10D30/6891; H10D30/6894; H10D64/00; H10D64/01; H10D64/031; H10D64/035
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
84 words
A method of fabrication a non-volatile semiconductor device comprising the steps of: forming a first spike which extends into a first region in a substrate; forming a first spike doped region in said first region through said spike; forming a dielectric layer over said substrate; forming a floating gate over said dielectric layer for storing charges; and doping said first region and a second region in said substrate, said first region extending toward said first spike to merge with said first spike doped region.
Claim 2
Independent Claim
84 words
A method of fabrication a non-volatile semiconductor device comprising the steps of: forming a first spike which extends into a first region in a substrate; forming a first spike doped region in said first region through said spike; forming a dielectric layer over said substrate; forming a floating gate over said dielectric layer for storing charges; and doping said first region and a second region in said substrate, said first region extending toward said first spike to merge with said first spike doped region.
Claim 3
Dependent Claim
38 words
The method of claim 1 further comprising the steps of: forming a gate dielectric over said floating gate; forming a control gate over said gate dielectric; and forming spacers on sidewalls of said floating and said control gates.
Claim 4
Dependent Claim
45 words
The method of claim 1 , wherein the first spike forming step includes the steps of: forming a mask over said substrate; forming an opening in said mask to expose a portion of said substrate; etching said exposed substrate portion to form said first spike.
Claim 5
Dependent Claim
34 words
The method of claim 3 , wherein the first spike forming step includes the step of forming spacers along sidewalls of said opening to reduce a width of said opening to a sub-lithographic size.
Claim 6
Dependent Claim
39 words
The method of claim 3 , wherein the etching step is performed using an etchant which preferentially etches along a selected crystal plane of the substrate to form said first spike having a tip that extends into said substrate.
Claim 7
Dependent Claim
39 words
The method of claim 1 , wherein the floating gate forming step forms said floating gate over a portion of said first region and over a channel portion of said substrate located between said first and said third regions.
Claim 8
Dependent Claim
25 words
The method of claim 1 , wherein the first spike forming step facilitates tunneling of said charges between said floating gate and said first region.
Claim 9
Dependent Claim
20 words
The method of claim 1 further comprising forming a first spike which extends into said second region in said substrate.
Claim 10
Dependent Claim
48 words
The method of claim 8 further comprising foaming a second spike which extends into said first region, said second spike being adjacent to said first spike, said first and second adjacent spikes having one tip pointing toward said floating gate and two tips pointing toward said first region.
Claim 11
Dependent Claim
49 words
The method of claim 9 further comprising forming a second spike which extends into said second region, said second spike being adjacent to said first spike, said first and second adjacent spikes having one tip pointing toward said floating gate and two tips pointing away from said second region.
Claim 12
Dependent Claim
94 words
The method of claim 1 , wherein the second spike forming step includes the steps of: forming a mask over said substrate; forming an opening in said mask to expose a portion of said substrate; forming spacers along sidewalls of said opening to reduce a width of said opening; forming a mask plug in said reduced opening; removing said spacers to exposed portions of said substrate; and etching said exposed substrate portions to form two adjacent spikes having one tip pointing toward said dielectric layer and two tips pointing away from said dielectric layer.
Claim 13
Dependent Claim
14 words
The method of claim 11 further comprising removing said mask and said mask plug.
Claim 14
Dependent Claim
20 words
The method of claim 11 , wherein the etching step preferentially etches along a selected crystal plane of the substrate.
Claim 15
Dependent Claim
45 words
The method of claim 10 , wherein the floating gate forming step forms said floating gate over a portion of said first region, a portion of said second region and over a channel portion of said substrate located between said first and said third regions.
Claim 16
Dependent Claim
37 words
The method of claim 10 , wherein the first and the second spike forming step Facilitates tunneling of said charges from said floating gate to said first region and from said first region to said floating gate.
References Cited (Backward Citations)
US5886373A
Cited
US6232633B1
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2005-01-14 | 2005-07-16 | 2006-01-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2009-01-14 | 2009-07-16 | 2010-01-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2013-01-14 | 2013-07-16 | 2014-01-15 | $7700.00 | Window Closed / Lapsed |