High temperature methods for enhancing retention characteristics of memory devices
AssigneeMacronix International Co., Ltd.
InventorsChao-I Wu, Tzu Hsuan Hsu
Life of this patent
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Abstract
Methods are described for improving the retention of a memory device by execution of a retention improvement procedure. The retention improvement procedure comprises a baking process of the memory device in a high temperature environment, a verifying process of the memory device that checks the logic state of memory cells, and a reprogramming process to program the memory device once again by programming memory cells in a 0-state to a high-Vt state. The baking step of placing the memory device in a high temperature environment causes a charge loss by expelling shallow trapped charges, resulting in the improvement of retention reliability.
Claims9
A method for improving retention characteristics of a memory device including a plurality of memory cells, comprising:
- baking the plurality of memory cells at a temperature level for a sufficient duration to cause shallow trapped charges to be expelled from the plurality of memory cells;
- after the baking step, verifying the plurality of memory cells to determine if written data in memory cells are unchanged from before the baking step;
- if the plurality of memory cells fail the verify step, reprogramming failing memory cells to the high threshold voltage state again;
- and
- after the reprogramming step, determining that the number of times that the memory cells have been reprogrammed is equal to or less than N number of times and returning to the baking step.
A method for improving retention characteristics of a memory device including a plurality of memory cells, comprising:
- programming and erasing the plurality of memory cells;
- excluding one or more memory cells in the plurality of memory cells that do not pass the programming and erasing steps;
- baking the memory cells at a temperature level for a sufficient duration to cause shallow trapped charges to be expelled from the memory cells;
- after the baking step, verifying the plurality of memory cells to determine if written data in the memory cells are unchanged from before the baking step;
- if the memory cells fail the verify step, reprogramming failed memory cells to the high threshold voltage state;
- and
- after the reprogramming step, determining that the number of times that the memory cells have been reprogrammed is equal to or less than N number of times and returning to the baking step.
Dependencies are inferred from the claim text.