US6172909B1
Expired / Lapsed
US
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Ramped gate technique for soft programming to tighten the Vt distribution
Assignee: Monterey Research LLC
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Filing: 1999-08-09
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Granted: 2001-01-09
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Expires: 2019-08-09
Abstract
Abstract A method to tighten the threshold voltage distribution curve in a memory device composed of multiple memory cells organized in rows and columns by soft programming each memory cell. Soft programming voltages that utilize the hot-carrier mechanism are selected and are applied sequentially to memory cells in wordlines. The soft programming voltages include a ramped voltage V GS of <3 volts, a V DS of <5 volts and a V sub of <0 volts. The soft programming voltages are applied for a time period of <10 microseconds. The V T distribution is reduced to a maximum width of <2 volts. The soft programming is applied to the memory cells after the memory cells have been verified as having been erased and a having been overerase corrected.
Inventors
- 👤 Sameer S. Haddad
- 👤 Janet S. Wang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 09:27
CPC Classifications
G; G11; G11C; G11C16/00; G11C16/02; G11C16/06; G11C16/34; G11C16/3404; G11C16/3409; G11C16/04; G11C16/0408; G11C16/0416; G11C16/3436; G11C16/344; G11C16/3445
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
122 words
A method to tighten the threshold voltage distribution curve in a memory device composed of multiple memory cells each having a source, drain, floating gate and control gate, wherein the memory cells are organized in rows and columns with the rows being wordlines and the columns being bitlines, the method comprising: applying soft programming voltages to the drains, sources and control gates of selected memory cells, wherein the soft programming voltages are as follows: a voltage less than 5 volts applied to the drains of the selected memory cells; a voltage less than 0 volts applied to the substrate of the selected memory cells; and a ramped voltage less than 3 volts applied to the control gates of the selected memory cells.
Claim 2
Independent Claim
122 words
A method to tighten the threshold voltage distribution curve in a memory device composed of multiple memory cells each having a source, drain, floating gate and control gate, wherein the memory cells are organized in rows and columns with the rows being wordlines and the columns being bitlines, the method comprising: applying soft programming voltages to the drains, sources and control gates of selected memory cells, wherein the soft programming voltages are as follows: a voltage less than 5 volts applied to the drains of the selected memory cells; a voltage less than 0 volts applied to the substrate of the selected memory cells; and a ramped voltage less than 3 volts applied to the control gates of the selected memory cells.
Claim 3
Dependent Claim
18 words
The method of claim 1 wherein the soft programming voltages are selected to utilize a hot-carrier injection mechanism.
Claim 4
Dependent Claim
26 words
The method of claim 2 wherein the initial voltage of the ramped control gate voltage is less than the threshold voltage of a least erased cell.
Claim 5
Dependent Claim
31 words
The method of claim 3 wherein the soft programming voltages are applied to the memory cells being soft programmed for a time period in the range of less than 10 μs.
Claim 6
Dependent Claim
31 words
The method of claim 4 wherein the soft programming voltages applied to the cells being soft programmed reduces a maximum width of the threshold voltage distribution to less than 2 volts.
Claim 7
Dependent Claim
25 words
The method of claim 1 further comprising verifying that all memory cells in the memory device have been erased before applying the soft programming voltages.
Claim 8
Dependent Claim
27 words
The method of claim 6 further comprising verifying that all memory cells in the memory device have been corrected for overerasure before applying the soft programming voltages.
Claim 9
Dependent Claim
124 words
A flash Electrically-Erasable Programmable Read-Only Memory (EEPROM), comprising: a plurality of memory cells each having a source, drain, floating gate, control gate and substrate; a power source for applying voltages to the drains, sources, substrates and control gates of selected memory cells; and a controller for controlling the power source to apply soft programming voltages to the drains, sources, substrates and control gates of the selected memory cells, wherein the power source applies a soft programming voltage of less than 5 volts to the drains of the selected memory cells, a soft programming voltage of less than 0 volts to the substrates of the selected memory cells, and a ramped voltage less than 3 volts to the control gates of the selected memory cells.
Claim 10
Dependent Claim
124 words
A flash Electrically-Erasable Programmable Read-Only Memory (EEPROM), comprising: a plurality of memory cells each having a source, drain, floating gate, control gate and substrate; a power source for applying voltages to the drains, sources, substrates and control gates of selected memory cells; and a controller for controlling the power source to apply soft programming voltages to the drains, sources, substrates and control gates of the selected memory cells, wherein the power source applies a soft programming voltage of less than 5 volts to the drains of the selected memory cells, a soft programming voltage of less than 0 volts to the substrates of the selected memory cells, and a ramped voltage less than 3 volts to the control gates of the selected memory cells.
Claim 11
Dependent Claim
25 words
The memory of claim 8 , in which the controller controls the power source to apply soft programming voltages to utilize a hot-carrier injection mechanism.
Claim 12
Dependent Claim
38 words
The memory of claim 9 , in which the controller controls the power source to apply a ramped voltage to the control gates having an initial voltage of less than the threshold voltage of a least erased cell.
Claim 13
Dependent Claim
32 words
The memory of claim 10 , in which the controller controls the power source to apply the soft programming voltages for a time period in the range of less than 10 μs.
References Cited (Backward Citations)
US5270980A
Cited
US5901090A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2004-01-09 | 2004-07-10 | 2005-01-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-01-09 | 2008-07-10 | 2009-01-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-01-09 | 2012-07-10 | 2013-01-09 | $7700.00 | Window Closed / Lapsed |