EP cycling dependent asymmetric/symmetric VPASS conversion in non-volatile memory structures
AssigneeSanDisk Technologies LLC
InventorsYu-Chung Lien, Xue Bai Pitner, Ken Oowada
Life of this patent
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Abstract
A method for programming a target memory cell of a memory array of a non-volatile memory system, the method comprises determining a total number of erase/programming (EP) cycles that were applied previously to the memory cell and, (1) if the determined total number of cycles does not exceed a threshold value, applying an asymmetric programming scheme, and, (2) if the determined total number of cycles exceeds the threshold value, applying a symmetric programming scheme. Further, a magnitude of a boosting voltage bias (VPASS) that is to be applied to an unselected word line may be determined according to the determined total number of erase/programming (EP) cycles.
Claims17
A method for programming a target memory cell of a memory array of a non-volatile memory system, comprising:
- determining a total number of erase/programming (EP) cycles applied previously to the target memory cell;
- comparing the total number of erase/programming (EP) cycles to a threshold value;
- and
- applying an asymmetric programming scheme as a result of determining that the total number of erase/programming (EP) cycles does not exceed a threshold value;
- and
- applying a symmetric programming scheme as a result of determining that the total number of erase/programming (EP) cycles exceeds the threshold value.
A non-volatile memory system, comprising:
- a memory array storing data in a target memory cell;
- and
- a memory controller coupled to the memory array and configured to:
- determine a total number of erase/programming (EP) cycles applied previously to the target memory cell;
- compare the total number of erase/programming (EP) cycles to a threshold value;
- apply an asymmetric programming scheme as a result of determining that the total number of erase/programming (EP) cycles do not exceed a threshold value;
- and
- apply a symmetric programming scheme as a result of determining that the total number of erase/programming (EP) cycles exceeds the threshold value.
A method for programming a target memory cell of a memory array of a non-volatile memory system, comprising:
- determining a total number of erase/programming (EP) cycles applied previously to the target memory cell;
- based upon the determined total number of erase/programming (EP) cycles, determining a magnitude of a boosting voltage bias (VPASS) to be applied to an unselected word linei
- wherein the magnitude of the boosting voltage bias (VPASS) is determined using a lookup table stored at the non-volatile memory system;
- wherein the lookup table comprises a succession of different benchmark numbers of total erase/programming (EP) cycles;
- wherein each benchmark number in turn corresponds to a magnitude of the boosting voltage bias (VPASS);
- and
- wherein the magnitude of the boosting voltage bias (VPASS) corresponding to a specific benchmark number is equal to, or greater than, the magnitude of the boosting voltage bias (VPASS) corresponding to the benchmark number immediately prior to the specific benchmark number in the succession .
The method according to claim [[14]] 13, wherein the lookup table comprises a series of different benchmark numbers of total erase/programming (EP) cycles, wherein each benchmark number in turn corresponds to a magnitude of the boosting voltage bias (VPASS).
Dependencies are inferred from the claim text.