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EP0690451A2
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Multistepped threshold convergence for a flash memory array
Assignee: Advanced Micro Devices Inc
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Filing: 1995-06-28
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Granted: —
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Expires: 2015-06-28
Abstract
Abstract A method of converging threshold voltages of memory cells in a flash EEPROM array after the memory cells have been erased, the method including applying a gate voltage (V G ) having an initial negative value which is increased to a more positive value in steps during application of a drain disturb voltage (V D ). By applying a gate voltage (V G ) with an initial negative value, leakage current during convergence is reduced enabling all cells on bit lines of the array to be converged in parallel.
Inventors
- 👤 Nader Radjy
- 👤 Lee E. Cleveland
- 👤 Jian Chen
- 👤 Shane Hollmer
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 16:32
CPC Classifications
G; G11; G11C; G11C16/00; G11C16/02; G11C16/06; G11C16/34; G11C16/3404; G11C16/3409; G11C16/10; G11C16/14; G11C16/16; G11C16/30
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
83 words
A method of converging threshold voltages of memory cells in a flash memory array after the memory cells have been erased, the method comprising successive steps of: setting a gate voltage to an initial value; applying a drain voltage to drains of the memory cells for a time period while applying the gate voltage to gates of the memory cells; and increasing the gate voltage in a positive direction and repeating the previous step if the gate voltage is below a predetermined value.
Claim 2
Dependent Claim
17 words
The method of claim 1, wherein the initial value of the gate voltage is a negative value.
Claim 3
Dependent Claim
49 words
The method of claim 1 or 2, wherein the time period during which the drain voltage is applied is long enough for cells to converge to a steady-state threshold voltage by hot-electron injection, but short enough to prevent cells from converging to the steady-state threshold voltage by hot-hole injection.
Claim 4
Dependent Claim
24 words
The method of claim 1, wherein the time period during which the drain voltage is applied is short enough to substantially prevent hot-hole injection.
Claim 5
Independent Claim
24 words
The method of any of claims 1 to 4, wherein the time period during which the drain voltage is applied is substantially 100 ms.
Claim 6
Independent Claim
29 words
The method of any of claims 1 to 5, wherein when the gate voltage reaches the predetermined value, the threshold voltages of the memory cells are above zero volts.
Claim 7
Dependent Claim
30 words
A flash memory array having a power supply controlled to apply the gate and drain voltages for converging threshold voltages of memory cells according to the method of claim 1.
Claim 8
Independent Claim
123 words
A method of converging threshold voltages of memory cells in a flash memory array after the memory cells have been erased, the method comprising successive steps of: applying a drain voltage to drains of the memory cells while applying a first gate voltage for a time period long enough to allow some memory cells to converge to a steady-state voltage, but short enough to prevent all cells which would converge to the steady-state voltage from converging; and applying the drain voltage to drains of the memory cells while applying a second gate voltage having a more positive value than the first gate voltage for a time period long enough to allow all memory cells which will converge to a steady-state voltage to converge.
Claim 9
Dependent Claim
59 words
The method of claim 8, wherein a power supply utilizes a charge pump to provide the drain voltage and the charge pump has a size required to supply the drain voltage which is less than a size required for a charge pump utilized to converge thresholds by applying the second step of claim 8 without applying the first step.
Claim 10
Dependent Claim
34 words
The method of claim 8, wherein current required to supply the drain voltage is less than current required to converge thresholds by applying the second step of claim 8 without applying the first step.
Claim 11
Independent Claim
106 words
A method of converging threshold voltages of memory cells in a flash memory array after the memory cells have been erased, the method comprising successive steps of: applying a drain voltage to drains of the memory cells while applying a plurality of gate voltage pulses, each gate voltage pulse after a first gate voltage pulse having a more positive value than a previous gate voltage pulse, each gate voltage pulse being applied for a time period long enough for cells to converge to a steady-state threshold voltage by hot-electron injection, but short enough to prevent cells from converging to the steady-state threshold voltage by hot-hole injection.
Claim 12
Dependent Claim
16 words
The method of claim 11, wherein the first gate voltage pulse applied has a negative value.
Claim 13
Dependent Claim
32 words
The method of claim 11 or 12, wherein after a last one of the plurality of gate voltage pulses is applied, the threshold voltages of the memory cells are above zero volts.
References Cited (Backward Citations)
No citation records indexed.
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