US5712814A
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Nonvolatile memory cell and a method for forming the same
Assignee: STMicroelectronics SRL
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Filing: 1995-07-18
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Granted: 1998-01-27
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Expires: 2015-07-18
Abstract
Abstract A nonvolatile memory having a cell comprising an N + type source region and drain region embedded in a P - type substrate and surrounded by respective P-pockets. The drain and source P-pockets are formed in two different high-angle boron implantation steps designed to optimize implantation energy and dosage for ensuring scalability of the cell and avoiding impairment of the snap-back voltage. The resulting cell also presents a higher breakdown voltage as compared with known cells.
Inventors
- 👤 Lorenzo Fratin
- 👤 Leonardo Ravazzi
- 👤 Carlo Riva
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 08:54
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/01; H10D30/021; H10D30/0411; H10D30/60; H10D30/68; H10D30/681; H10D62/00; H10D62/10; H10D62/17; H10D62/213; H10D62/221; H10D62/235; H10D62/299; H10D62/307
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
116 words
An EPROM and flash-EEPROM nonvolatile memory comprising a memory cell having drain and source regions of a first conductivity type and embedded in a substrate having a second opposite conductivity type and a first doping agent concentration level, said substrate forming a channel region separating said drain and source regions; and a drain pocket surrounding said drain region towards said channel region and having said second opposite conductivity type and a second doping agent concentration level; characterized in that it comprises a source pocket surrounding said source region and having said second opposite conductivity type and a third doping agent concentration level differing from said first and second levels; said source pocket forming snap-back reducing means.
Claim 2
Dependent Claim
116 words
An EPROM and flash-EEPROM nonvolatile memory comprising a memory cell having drain and source regions of a first conductivity type and embedded in a substrate having a second opposite conductivity type and a first doping agent concentration level, said substrate forming a channel region separating said drain and source regions; and a drain pocket surrounding said drain region towards said channel region and having said second opposite conductivity type and a second doping agent concentration level; characterized in that it comprises a source pocket surrounding said source region and having said second opposite conductivity type and a third doping agent concentration level differing from said first and second levels; said source pocket forming snap-back reducing means.
Claim 3
Dependent Claim
28 words
A memory as claimed in claim 1, characterized in that said first conductivity type is an N type, and said second opposite conductivity type is a P type.
Claim 4
Dependent Claim
42 words
A memory as claimed in claim 2, characterized in that said doping agents of said drain and source pockets comprise boron; said doping agent of said drain region comprises arsenic; and said doping agent of said source region comprises arsenic and phosphorus.
Claim 5
Dependent Claim
33 words
A memory as claimed in claim 1, characterized in that said third concentration level is higher than said first concentration level; and said second concentration level is higher than said third concentration level.
Claim 6
Dependent Claim
49 words
A memory as claimed in claim 4, wherein said substrate presents a surface over which stacked gate regions extend; characterized in that said source region is farther from said surface than said drain region; and said source pocket extends a greater distance from said surface than said drain pocket.
Claim 7
Dependent Claim
49 words
A memory as claimed in claim 1, characterized in that said drain pocket presents a total high-angle implantation dose ranging between 1×10 13 and 1×10 14 atoms/cm 2 , and said source pocket presents a total high-angle implantation dose ranging between 5×10 11 and 5×10 12 atoms/cm 2 .
Claim 8
Dependent Claim
39 words
A memory as claimed in claim 1, characterized in that said drain pocket presents a high-angle implantation energy ranging between 30 and 100 KeV, and said source pocket presents a high-angle implantation energy ranging between 80 and 130 KeV.
Claim 9
Dependent Claim
25 words
A memory as claimed in claim 1, characterized in that said drain and source pockets are implanted at an angle ranging between 30° and 60°.
Claim 10
Dependent Claim
90 words
A nonvolatile memory cell formed in a substrate of a second type of semiconductor material, comprising: a drain of a first type of semiconductor material; a source of said first type of semiconductor material; a drain pocket of said second type of semiconductor material that is contiguous with a portion of said drain and has a first impurity concentration; and a source pocket of said second type of semiconductor material that is contiguous with a portion of said source and has a second impurity concentration different than said first concentration.
Claim 11
Dependent Claim
90 words
A nonvolatile memory cell formed in a substrate of a second type of semiconductor material, comprising: a drain of a first type of semiconductor material; a source of said first type of semiconductor material; a drain pocket of said second type of semiconductor material that is contiguous with a portion of said drain and has a first impurity concentration; and a source pocket of said second type of semiconductor material that is contiguous with a portion of said source and has a second impurity concentration different than said first concentration.
Claim 12
Dependent Claim
24 words
The cell of claim 9 wherein: said drain comprise arsenic; said source comprise arsenic and phosphorous; and said drain and source pockets comprise boron.
Claim 13
Dependent Claim
15 words
The cell of claim 9 wherein said first impurity concentration exceeds said second impurity concentration.
Claim 14
Dependent Claim
23 words
The cell of claim 9 wherein: said source is deeper than said drain; and said source pocket is deeper than said drain pocket.
Claim 15
Dependent Claim
25 words
The cell of claim 9 wherein: said first type of semiconductor material is donor type; and said second type of semiconductor material is acceptor type.
Claim 16
Dependent Claim
18 words
The nonvolatile memory of claim 1 wherein the drain pocket is asymmetrical with respect to the source pocket.
Claim 17
Dependent Claim
18 words
The nonvolatile memory of claim 1 wherein the drain region is asymmetrical with respect to the source region.
Claim 18
Dependent Claim
81 words
A nonvolatile memory cell, comprising: a drain having a first conductivity, the drain disposed in a substrate having a second conductivity; a source disposed in the substrate and having the first conductivity; a drain pocket disposed in the substrate and having the second conductivity, the drain pocket being contiguous with and being deeper than the drain; and a source pocket disposed in the substrate and having the second conductivity, the source pocket being contiguous with and being deeper than the source.
Claim 19
Dependent Claim
81 words
A nonvolatile memory cell, comprising: a drain having a first conductivity, the drain disposed in a substrate having a second conductivity; a source disposed in the substrate and having the first conductivity; a drain pocket disposed in the substrate and having the second conductivity, the drain pocket being contiguous with and being deeper than the drain; and a source pocket disposed in the substrate and having the second conductivity, the source pocket being contiguous with and being deeper than the source.
Claim 20
Dependent Claim
33 words
The nonvolatile memory cell of claim 16 wherein: the drain pocket has a first impurity concentration; and the source pocket has a second impurity concentration that is different from the first impurity concentration.
Claim 21
Dependent Claim
33 words
The nonvolatile memory cell of claim 16 wherein: the drain pocket has a first impurity concentration; and the source pocket has a second impurity concentration that is less than the first impurity concentration.
Claim 22
Dependent Claim
15 words
The nonvolatile memory cell of claim 16 wherein the source is deeper than the drain.
Claim 23
Dependent Claim
17 words
The nonvolatile memory cell of claim 16 wherein the source pocket is deeper than the drain pocket.
Claim 24
Dependent Claim
21 words
The nonvolatile memory cell of claim 16 wherein: the first conductivity is N type; and the second conductivity is P type.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 2001-01-26 | 2001-07-28 | 2002-01-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-01-26 | 2005-07-28 | 2006-01-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-01-26 | 2009-07-28 | 2010-01-27 | $7700.00 | Window Closed / Lapsed |