Memory device and operating method thereof
There are provided a memory device and an operating method thereof. A memory device includes: a peripheral circuit for decreasing threshold voltages of memory cells included in a selected memory block and then performing an erase verify operation for detecting a threshold voltage distribution of the memory cells, wherein the peripheral circuit applies an erase pulse to a well, bit lines or source line in which the selected memory block is included a preset number of times; and a control logic for outputting a voltage setup code according to the threshold voltage distribution of an erase status, which is detected by the erase verify operation.
1. A memory device comprising:
a peripheral circuit configured to decrease threshold voltages of memory cells included in a selected memory block and then perform an erase verify operation for detecting a threshold voltage distribution of the memory cells, wherein the peripheral circuit applies an erase pulse to a well, bit lines or a source line included in the selected memory block a preset number of times; and
a control logic configured to output a voltage setup code according to the threshold voltage distribution of an erase status, which is detected by the erase verify operation,
wherein, when the erase verify operation is performed, the peripheral circuit uses an erase verify voltage that is gradually decreased.
2. The memory device of claim 1 , wherein, when the erase pulse is applied to the well, the bit lines or the source line plural times, the peripheral circuit consecutively applies the erase pulse to the well.
3. The memory device of claim 1 , wherein the erase verify voltage is gradually decreased by an offset from a preset erase verify voltage.
4. The memory device of claim 3 , wherein, if the erase verify operation passes, the peripheral circuit performs the erase verify operation, using an erase verify voltage that is lower by the offset than the erase verify voltage at which the erase verify operation passes.
5. The memory device of claim 3 , wherein the control logic controls the peripheral circuit such that the erase verify operation is repeated while gradually decreasing the erase verify voltage until the erase verify operation fails.
6. The memory device of claim 5 , wherein, if the erase verify operation fails, the control logic controls the peripheral circuit to store erase status information corresponding to the erase verify voltage used in erase verify operation that fails in flag cells of the selected memory block.
7. The memory device of claim 6 , wherein the control logic includes an erase status determining circuit configured to determine the threshold voltage distribution of the erase status, based on the erase status information, in a program operation.
8. The memory device of claim 7 , wherein the erase status determining circuit selects the voltage setup code, based on the erase status information.
9. The memory device of claim 7 , wherein the control logic includes a voltage setup code table in which various different voltage setup codes are stored, to output the voltage setup code.
10. The memory device of claim 3 , wherein, when the erase verify operation fails, the peripheral circuit performs the erase verify operation, using an erase verify voltage gradually increased by an offset as compared with a current erase verify voltage.
11. The memory device of claim 10 , wherein, when the erase verify operation fails until the use number of the erase verify voltage reaches a preset erase verify number, the peripheral circuit additionally performs an operation of decreasing the threshold voltages of the memory cells.
12. The memory device of claim 11 , wherein the peripheral circuit repeats the operation of decreasing the threshold voltages of the memory cells and the erase verify operation until the erase verify operation passes.
13. The memory device of claim 1 , wherein the peripheral circuit sets a program verify voltage according to the voltage setup code.
14. The memory device of claim 1 , wherein the control logic selectively outputs the voltage setup code such that a program verify voltage is set lower as the threshold voltage distribution of the selected memory block becomes lower.
15. The memory device of claim 1 , wherein, when a program operation is performed, the peripheral circuit generates a program verify voltage according to the voltage setup code.
16. A method for operating a memory device, the method comprising:
applying an erase pulse to a selected memory block;
after the erase pulse is applied, setting a program verify voltage according to an erase status of the selected memory block; and
performing a program operation of the selected memory block, using the program verify voltage,
wherein the setting of the program verify voltage includes performing an erase verify operation, using an erase verify voltage that is gradually decreased.
17. The method of claim 16 , wherein, in the applying of the erase pulse to the selected memory block, the erase pulse is applied to a well, bit lines or a source line included in the selected memory block.
18. The method of claim 17 , wherein, when the erase pulse is applied to the well, the bit lines or the source line plural times, the erase pulse is consecutively applied to the well, the bit lines or the source line.
19. The method of claim 16 , wherein the setting of the program verify voltage further includes:
if the erase verify operation fails, store erase status information in the selected memory block according to the erase verify voltage used in the erase verify operation that fails;
outputting a voltage setup code, based on the erase status information, in a program operation; and
setting the program verify voltage according to the output voltage setup code.
20. The method of claim 19 , wherein the erase verify operation:
passes if threshold voltages of all memory cells included in the selected memory block are lower than the erase verify voltage; and
fails if a memory cell of which erase verify voltage is higher than the erase verify voltage is detected among the memory cells included in the selected memory block.
21. The method of claim 19 , wherein, if the erase verify operation passes, the erase verify voltage is decreased by an offset voltage, and the erase verify operation is again performed.
22. The method of claim 21 , wherein the erase verify operation is consecutively performed until the erase verify operation fails.
23. A method for operating a memory device, the method comprising:
performing an erase operation on memory cells;
setting a program verify voltage according to threshold voltages of the erased memory cells; and
performing a program operation on the erased memory cells, using the program verify voltage,
wherein the performing of the erase operation includes storing erase status information of the memory cells in flag cells according to the threshold voltages of the erased memory cells.
24. The method of claim 23 , wherein the performing of the erase operation further includes consecutively applying an erase pulse to a well, bit lines or a source line included in the memory cells up to a certain number of times.
25. The method of claim 24 , wherein, in the setting of the program verify voltage, the program verify voltage is set in response to a voltage setup code selected based on the erase status information among a plurality of different voltage setup codes.
26. The method of claim 25 , wherein the program operation is performed using the program verify voltage set according to the voltage setup code and a preset program voltage.
27. A method for operating a memory device, the method comprising:
applying an erase pulse to a selected memory block;
after the erase pulse is applied, setting a program verify voltage according to an erase status of the selected memory block; and
performing a program operation of the selected memory block, using the program verify voltage,
wherein the setting of the program verify voltage includes performing an erase verify operation, using a gradually increased erase verify voltage.
28. The method of claim 27 , wherein the setting of the program verify voltage further includes:
when the erase verify operation passes, storing erase status information in the selected memory block according to the erase verify voltage used in the passed erase verify operation;
outputting a voltage setup code, based on the erase status information, in a program operation; and
setting the program verify voltage according to the output voltage setup code.
29. The method of claim 28 , wherein, when the erase verify operation fails, the erase verify operation is performed, using an erase verify voltage increased by an offset as compared with a current erase verify voltage.
30. The method of claim 29 , wherein, when the erase verify operation fails until the use number of the erase verify voltage reaches a preset erase verify number, an operation of decreasing the threshold voltages of the memory cells is additionally performed.
31. The method of claim 29 , wherein the erase verify operation is performed until the erase verify operation passes.