Programming of nonvolatile memory cells
First Claim
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1. A method for programming a multi-level NROM cell having more than one programmed state to a target programmed state, the method comprising:
- applying a drain, a source and a gate voltage to said cell;
verifying a threshold voltage level of said cell; and
if verified threshold voltage level is below a threshold voltage level associated with said target programmed state;
increasing said drain voltage; and
maintaining said gate voltage at a constant level during at least a part of said step of increasing, and repeating said steps of applying, verifying, increasing and maintaining until said cell'"'"'s threshold voltage level is substantially equal to the threshold voltage level associated with said target programmed state.
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Abstract
A method for programming an NROM cell which includes the steps of applying a drain, a source and a gate voltage to the cell and verifying a programmed or a non-programmed state of the cell. If the cell is in the non-programmed state, the method includes the steps of increasing the drain voltage and maintaining the gate voltage at a constant level during at least a part of the step of increasing. The steps of applying, verifying, increasing and maintaining are repeated until the cell reaches the programmed state.
246 Citations
41 Claims
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1. A method for programming a multi-level NROM cell having more than one programmed state to a target programmed state, the method comprising:
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applying a drain, a source and a gate voltage to said cell;
verifying a threshold voltage level of said cell; and
if verified threshold voltage level is below a threshold voltage level associated with said target programmed state;
increasing said drain voltage; and
maintaining said gate voltage at a constant level during at least a part of said step of increasing, and repeating said steps of applying, verifying, increasing and maintaining until said cell'"'"'s threshold voltage level is substantially equal to the threshold voltage level associated with said target programmed state. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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2. A method for controlling the programming time of a multi-level NROM cell having more than one programmed state to a target programmed state, the method comprising:
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applying a drain, a source and a gate voltage to said cell;
verifying a threshold voltage level of said cell; and
if verified threshold voltage level is below a threshold voltage level associated with said target programmed state;
increasing said drain voltage; and
maintaining said gate voltage at a constant level during at least a part of said step of increasing, and repeating said steps of applying, verifying, increasing and maintaining until said cell'"'"'s threshold voltage level is substantially equal to the threshold voltage level associated with said target programmed state.
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16. A method for confining charge within a predefined region of a retention layer of a multi-level NROM cell having more than one programmed state and having a gate, the method comprising, during programming to a target programmed state one storage area of said cell;
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applying an incrementally increasing drain voltage to a diffusion area acting as a drain of said cell;
maintaining a constant gate voltage on said gate during at least a part of said step of applying;
verifying a threshold voltage level of said cell; and
if verified threshold voltage level is below a threshold voltage level associated with said target programmed state, repeating said steps of applying, maintaining and verifying until said cell substantially reaches the threshold voltage level associated with said target programmed state. - View Dependent Claims (20, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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17. A method for retaining charge in a multi-level NROM cell having more than one programmed state and having a gate and a retention layer, the method comprising:
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confining said charge within a predefined region of said retention layer of said cell by;
applying an incrementally increasing drain voltage to a diffusion area acting as a drain of said cell;
maintaining a constant gate voltage on said gate during at least a part of said step of applying;
verifying a threshold voltage level of said cell; and
if verified threshold voltage level is below a threshold voltage level associated with a target programmed state, repeating said steps of confining and verifying until said cell'"'"'s threshold voltage level substantially reaches the threshold voltage level associated with said target programmed state.
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18. A method for retaining charge in a multi-level NROM cell having more than one programmed state and having a gate and a retention layer, the method comprising:
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providing a compact spatial charge distribution within a predefined region of said retention layer of said cell by;
applying an incrementally increasing drain voltage to a diffusion area acting as a drain of said cell;
maintaining a constant gate voltage on said gate during at least a part of said step of applying;
verifying a threshold voltage level of said cell; and
if verified threshold voltage level is below a threshold voltage level associated with a target programmed state, repeating said steps of providing and verifying until said cell'"'"'s threshold voltage level substantially reaches the threshold voltage level associated with said target programmed state. - View Dependent Claims (34, 35)
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19. A method for retaining the separation distance between two charge regions in a multi-level NROM cell having more than one programmed state and having a gate and two diffusion areas, the method comprising, for each charge region:
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applying an incrementally increasing drain voltage to the diffusion area closest to said charge region;
maintaining a constant gate voltage on said gate during at least a part of said step of applying;
verifying a threshold voltage level of said cell; and
if verified threshold voltage level is below a threshold voltage level associated with a target programmed state, repeating said steps of applying, maintaining and verifying until said cell'"'"'s threshold voltage level substantially reaches the threshold voltage level associated with said target programmed state. - View Dependent Claims (24)
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36. A method for programming a multi-level NROM cell having more than one programmed state to a target programmed state, the method comprising, during programming:
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applying a drain, a source and a gate voltage; and
while keeping said gate voltage at at least one constant level, increasing said drain voltage until said cell substantially reaches saturation.
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37. A method for controlling a change in the threshold voltage of a multi-level NROM cell having more than one programmed state, wherein the cell receives a drain, a source and a gate voltage, the method comprising, during programming to a target programmed state, varying said drain voltage while keeping said gate voltage at at least one constant level.
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38. A method for controlling the programming time of a multi-level NROM cell having more than one programmed state to a target programmed state, the method comprising:
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applying a drain, a source and a gate voltage; and
while keeping said gate voltage at at least one constant level, incrementally increasing said drain voltage during programming, until said cell reaches saturation.
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39. A method for programming an array of multi-level NROM cells having more than one programmed state and having varying programming speeds, the array having bit lines and word lines, the method comprising:
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providing a gate voltage to one of said word lines;
providing a source voltage to a first bit line and a drain voltage to a second bit line; and
varying said drain voltage while keeping said gate voltage at a constant level until said array of cells reach saturation.
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40. A method for retaining the separation distance between two charge regions in a multi-level NROM cell, the multi-level NROM cell having more than one programmed state and having a gate and two diffusion areas, the method comprising, while applying at least one constant gate voltage to said gate, for each charge region, applying an incrementally increasing bit line voltage to the diffusion area closest to said charge region, until said cell reaches saturation.
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41. A method for retaining charge in a multi-level NROM cell having more than one programmed state and having a gate and a retention layer, the method comprising providing a compact spatial charge distribution within a predefined region of said retention layer of said cell by applying an incrementally increasing bit line voltage to a diffusion area acting as a drain of said cell, while applying at least one constant gate voltage to said gate, until said cell reaches saturation.
Specification