Vierra Magen Marcus LLP
Method to recover cycling damage and improve long term data retention
Techniques for reversing damage caused by program-erase cycles in charge-trapping memory to improve long term data retention. A recovery process improves the data retention of a block of memory cells by programming the memory cells to a relatively high threshold voltage and enforcing a time period of several minutes or hours in which the memory cells are inactive and remain at the relatively high Vth levels. Damage such as traps in the memory cells is essentially healed or annealed out during this inactive period. All of the memory cells can be healed at the same time and by relatively equal amounts. At the conclusion of the recovery process, the block is returned to a pool of available blocks. In one approach, an amount of recovery is measured and the period of inactivity is continued for an amount of time which is based on the amount of recovery.
SanDisk Technologies Inc.
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Wei Zhengyi Yingda Jian Ching-Huang
Zhao Zhang Dong Chen Lu