Dynamic healing of non-volatile memory cells
View Patent ↗Methods and systems are disclosed for dynamic healing of non-volatile memory (NVM) cells within NVM systems. The dynamic healing embodiments described herein relax damage within tunnel dielectric layers for NVM cells that occurs over time from charges (e.g., holes and/or electrons) becoming trapped within these tunnel dielectric layers. NVM operations with respect to which dynamic healing processes can be applied include, for example, erase operations, program operations, and read operations. For example, dynamic healing can be applied where performance for the NVM system degrades beyond a selected performance level for an NVM operation, such as elevated erase/program pulse counts for erase/program operations and bit errors for read operations. A variety of healing techniques can be applied, such as drain stress processes, gate stress processes, and/or other desired healing techniques.
1. A method for dynamic healing of non-volatile memory (NVM) cells, comprising:
performing a memory operation for one or more non-volatile memory (NVM) cells within an NVM system, each NVM cell having a tunnel dielectric layer, a drain node, a source node, and at least one gate node;
determining performance information related to the memory operation; and
applying a healing process to the NVM cells if performance for the NVM cells has degraded beyond a selected performance level based upon the performance information;
wherein the applying step comprises at least one of applying a drain stress voltage to the drain nodes for the NVM cells or applying a gate stress voltage to the gate nodes for the NVM cells; and
wherein the healing process is configured to heal damage to the tunnel dielectric layers within the NVM cells.
2. The method of claim 1 , wherein the applying step is performed while junction temperatures within the NVM cells are at elevated temperature levels.
3. The method of claim 1 , wherein the memory operation comprises at least one of an erase operation or a program operation, wherein the performance information comprises an erase pulse count if the memory operation comprises the erase operation, and wherein the performance information comprises a program pulse count if the memory operation comprises the program operation.
4. The method of claim 1 , wherein the memory operation comprises a read operation and wherein the performance information comprises a bit error detected for the read operation.
5. The method of claim 1 , wherein after the healing process is applied, repeating the performing, determining, and applying steps until performance for the NVM cells is determined to meet the selected performance level.
6. The method of claim 1 , further comprising repeating the performing, determining, and applying steps over time and adjusting the selected performance level after one or more applying steps have been performed.
7. The method of claim 1 , further comprising determining if healing is enabled before performing the determining and applying steps.
8. The method of claim 7 , further comprising allowing healing to be independently enabled for two or more blocks of NVM cells.
9. The method of claim 1 , wherein the drain stress voltage, if applied, comprises a voltage of 3.0 volts to 5.0 volts applied for 1 to 100 seconds.
10. The method of claim 1 , wherein the gate stress voltage, if applied, comprises a voltage of 6.0 volts to 9.0 volts applied for 1 to 100 seconds.
11. A non-volatile memory (NVM) system, comprising:
an array of non-volatile memory (NVM) cells, each NVM cell having a tunnel dielectric layer, a drain node, a source node, and at least one gate node;
controller circuitry configured to perform a memory operation for one or more of the NVM cells, to determine performance information for the memory operation, and to apply a healing process to the NVM cells if performance for the NVM cells has degraded beyond a selected performance level based upon the performance information;
wherein the controller circuitry is further configured to apply at least one of a drain stress voltage to the drain nodes for the NVM cells as the healing process or a gate stress voltage to the gate nodes for the NVM cells as the healing process; and
wherein the healing process is configured to heal damage to the tunnel dielectric layers within the NVM cells.
12. The NVM system of claim 11 , wherein the memory operation comprises an erase operation and wherein the performance information comprises an erase pulse count for the erase operation.
13. The NVM system of claim 11 , wherein the memory operation comprises a program operation and wherein the performance information comprises a program pulse count for the program operation.
14. The NVM system of claim 11 , wherein the memory operation comprises a read operation and wherein the performance information comprises a bit error detected for the read operation.
15. The NVM system of claim 11 , wherein the controller circuitry is further configured to determine if healing is enabled before the healing process is applied.
16. The NVM system of claim 15 , wherein the controller circuitry is further configured to independently determine if healing is enabled for one or more blocks of NVM cells.
17. The NVM system of claim 11 , wherein the drain stress voltage comprises a voltage of 3.0 volts to 5.0 volts applied for 1 to 100 seconds, if the controller circuitry is configured to apply a drain stress voltage.
18. The NVM system of claim 11 , wherein the gate stress voltage comprises a voltage of 6.0 volts to 9.0 volts applied for 1 to 100 seconds, if the controller circuitry is configured to apply a gate stress voltage.
19. The NVM system of claim 11 , wherein the controller circuitry is further configured to repeat the healing process until performance for the NVM cells is determined to meet the selected performance level.
20. The NVM system of claim 11 , wherein the controller circuitry is further configured to adjust the selected performance level after one or more healing processes have been applied.