Method to recover cycling damage and improve long term data retention

摘要

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.

主权项

1. A method for operating a memory device, comprising:
determining that memory cells in a block have been subject to a specified amount of usage, the memory cells in the block store data in different data states including an erased state and a highest data state, the erased state is represented by a respective threshold voltage distribution and the highest data state is represented by a respective threshold voltage distribution which is higher than the respective threshold voltage distribution of the erased state; and in response to the determining, performing a data recovery process for the memory cells, the performing the data recovery process comprises erasing the block, programming the memory cells, wherein the memory cells are programmed to a threshold voltage distribution which is at least as high as the respective threshold voltage distribution of the highest data state, and enforcing a time period of at least ten minutes in which detrapping occurs for the memory cells while programming of the block is not allowed and erasing of the block is not allowed.