Erase system and method of nonvolatile memory device
An erase system and method of a nonvolatile memory device includes supplying an erase voltage to a plurality of memory cells of a nonvolatile memory, performing a read operation with a read voltage to word lines of the plurality of memory cells, and performing an erase verification operation with an erase verification voltage to at least one of the word lines of the plurality of memory cells, the erase verification voltage lower than the read voltage.
1. An erase method of a nonvolatile memory device, the erase method comprising:
supplying an erase voltage to a plurality of memory cells;
performing a read operation with a read voltage to word lines of the plurality of memory cells; and
performing an erase verification operation with an erase verification voltage to at least one of the word lines of the plurality of memory cells, the erase verification voltage lower than the read voltage, wherein
the plurality of memory cells comprises at least one dummy cell and one or more regular memory cells, and the at least one dummy cell is supplied with a voltage different from an operating voltage, which is supplied to the regular memory cells, in the reading operation and the erase verification operation.
2. The erase method of claim 1 , wherein the read voltage comprises one or more levels of voltages to be applied to the respective word lines.
3. The erase method of claim 1 , wherein the read voltage comprises a single level of a voltage to be applied to the word lines.
4. The erase method of claim 1 , wherein:
the erase verification voltage is variable with respect to a corresponding one of the word lines of the plurality of memory cells; and
the variable erase verification voltage is lower than the read voltage.
5. The erase method of claim 1 , wherein the read voltage is higher than a voltage of a threshold voltage of a program state of the plurality of memory cells.
6. An erase method of a nonvolatile memory device, the erase method comprising:
supplying an erase voltage to a plurality of strings each having a plurality of memory cells;
performing a read operation with a read voltage to word lines of the plurality of memory cells;
determining one or more strings as an off strung string according to the performed read operation;
processing an erase verification pass on the off string; and
performing an erase verification operation with an erase verification voltage to word lines of the plurality of strings.
7. The erase method of claim 6 , further comprising:
supplying a modified erase voltage to the plurality of strings according to the performed erase verification operation.
8. The erase method of claim 7 , wherein:
the plurality of memory cells are determined as an off string and a non off string according to the read operation; and
the erase verification operation includes preventing a bitline pre-charging operation from being performed on the off string.
9. The erase method of claim 6 , further comprising:
supplying different voltages to bit lines of the off string and the non off string as pre-charging voltage; and
supplying the erase verification voltage to the respective word lines of the plurality of memory cells in the erase verification operation.
10. The erase method of claim 6 , wherein:
the plurality of memory cells comprises at least one dummy cell and one or more regular memory cells; and
the at least one dummy cell is supplied with a voltage different from an operating voltage which is supplied to the regular memory cells, in the reading operation and the erase verification operation.
11. A memory system comprising:
a nonvolatile memory device comprising a memory cell array having a substrate and a plurality of strings each having a plurality of memory cells, the plurality of strings formed on the substrate in a direction perpendicular to the substrate; and
a controller to generate a command to perform an erase operation on the nonvolatile memory device, such that the nonvolatile memory device:
erases the plurality of strings;
performs a read operation with a read voltage to word lines of the plurality of memory cells;
determines one or more strings as an off string according to the performed read operation;
processes an erase verification pass on the off string; and
performs an erase verification operation with an erase verification voltage to word lines of the plurality of strings, the erase verification voltage lower than the read voltage.
12. The memory system of claim 11 , wherein the strings are spaced apart from each other by a gap in which a channel film unit is formed to connect the memory cells of the string, and the channel film unit has a defect to cause the off string.
13. The memory system of claim 12 , wherein the nonvolatile memory device comprises a channel film unit connected to the adjacent strings, and the off string is formed with the channel film unit which has no electrical contact with the substrate.
14. The memory system of claim 12 , wherein the nonvolatile memory device comprises a drain and a channel film unit connected to the string, and the off string is formed with the channel film unit which has no electrical contact with the substrate.
15. The memory system of claim 11 , wherein the nonvolatile memory device prevents the erase verification operation from performing on the off string of the first determination.