Nonvolatile memory device and method of operating the same
According to example embodiments, an operation method of a nonvolatile memory device includes determining a location of a selected word line among word lines connected to the nonvolatile memory device, selecting one of a plurality of different read disturbance reducing modes according to the location of the selected word line, and performing a read or verification operation according to the selected read disturbance reducing modes. The nonvolatile memory device includes cell strings. Each one of the cell strings includes memory cells stacked on top of each other in a direction perpendicular to the substrate and between a ground select transistor and a string select transistor. The ground select transistor is between the substrate and the number of the memory cells. The string select transistor is connected to a bit line and is between the bit line and the number of the memory cells.
1. A nonvolatile memory device, comprising:
a cell string connected to a bit line and a string selection line, the cell string including a plurality of memory cells connected in series, the plurality of memory cells being connected to a plurality of word lines, respectively and stacked in a direction perpendicular to a substrate;
a voltage generator configured to provide a pre-pulse voltage to a selected word line or the string selection line before sensing memory cells; and
a control logic configured to control a read operation or a program verify operation such that their operation modes for providing the pre-pulse voltage are different from each other.
2. The nonvolatile memory device of claim 1 , wherein the string selection line is an unselected string selection line.
3. The nonvolatile memory device of claim 1 , wherein the operation modes for providing the pre-pulse voltage are different according to a location of the selected word line.
4. The nonvolatile memory device of claim 3 , wherein the control logic is configured to determine the location of the selected word line, select one of the operation modes according to the location of the selected word line, and to performs the read operation or the program verify operation according to the selected operation mode.
5. The nonvolatile memory device of claim 1 , wherein the pre-pulse voltage is a turn-on voltage that is sufficient to turn on the memory cells.
6. The nonvolatile memory device of claim 5 , wherein
the cell string is connected to a ground selection line, and
the voltage generator is configured to provide the turn-on voltage to the ground selection line while applying the pre-pulse voltage to the string selection line or the selected word line.
7. The nonvolatile memory device of claim 1 , wherein the operation modes for providing the pre-pulse voltage include a selected word line pre-pulse (SWPP) mode and an unselected string select line pre-pulse (USPP) mode.
8. The nonvolatile memory device of claim 7 , wherein
the voltage generator is configured to provide the pre-pulse voltage to the selected word line before applying a read voltage to the selected word line in the SWPP mode, and
the voltage generator is configured to provide the pre-pulse voltage to the string selection line before applying a turn-off voltage to the string selection line in the USPP mode.
9. The nonvolatile memory device of claim 1 , wherein the nonvolatile memory device includes at least one flash memory having a three-dimensional structure in which memory cells are stacked in the direction perpendicular to the substrate.
10. A program verify method of a nonvolatile memory device which includes a cell string connected to a bit line and a string selection line, the cell string including a plurality of memory cells connected in series, the plurality of memory cells being connected to a plurality of word lines, respectively and stacked in a direction perpendicular to a substrate, the program verify method comprising:
determining a location of a selected word line;
selecting one of a plurality of operation modes for reducing read disturbance of the cell string according to the location of the selected word line; and
performing a program verify operation according to the selected operation mode.
11. The program verify method of claim 10 , wherein
the operation modes for reducing read disturbance of the cell string include a selected word line pre-pulse (SWPP) mode and an unselected string select line pre-pulse (USPP) mode,
the SWPP mode includes applying a pre-pulse voltage to the selected word line before applying a read voltage to the selected word line, and
the USPP mode include applying the pre-pulse voltage to the string selection line before applying a turn-off voltage to the string selection line in the USPP mode.
12. The program verify method of claim 11 , wherein the selected word line is included in one of lower word lines adjacent to a common source line, included in one of upper word lines adjacent to the string select line, or included in one of middle word lines between the lower word lines and the upper word lines.
13. The program verify method of claim 12 , wherein the selected operation mode is the SWPP mode when the selected word line is included in one of the lower word lines.
14. The program verify method of claim 13 , wherein the selected operation mode is the USPP mode when the selected word line is included in one of the upper word lines.
15. The program verify method of claim 12 , wherein the selected operation mode is the USPP mode when the selected word line is included in one of the lower word lines.
16. A read method of a nonvolatile memory device which includes a cell string connected to a bit line and a string selection line, the cell string including a plurality of memory cells connected in series, the plurality of memory cells being connected to a plurality of word lines, respectively and stacked in a direction perpendicular to a substrate, the read method comprising:
selecting one of a plurality of operation modes for reducing read disturbance of the cell string;
applying a pre-pulse voltage to the string selection line or a selected word line according to the selected operation mode; and
applying a read voltage to the selected word line and a read pass voltage to unselected word lines.
17. The read method of claim 16 , further comprising:
determining a location of the selected word line,
wherein the selected one of the plurality of operation modes includes selecting the one of the plurality of operation modes according to the location of the selected word line.
18. The read method of claim 17 , wherein
the operation modes for reducing read disturbance of the cell string include a selected word line pre-pulse (SWPP) mode and an unselected string select line pre-pulse (USPP) mode,
the SWPP mode includes applying a pre-pulse voltage to the selected word line before applying a read voltage to the selected word line, and
the USPP mode includes applying the pre-pulse voltage to the string selection line before applying a turn-off voltage to the string selection line.
19. The read method of claim 18 , wherein the selected word line is included in one of lower word lines adjacent to a common source line, included in one of upper word lines adjacent to the string select line, or included in one of middle word lines between the lower word lines and the upper word lines.
20. The read method of claim 19 , wherein the selected operation mode is the SWPP mode when the selected word line is included in one of the lower word lines.
21. The read method of claim 19 , wherein the selected operation mode is the USPP mode when the selected word line is included in one of the lower word lines.
22. The read method of claim 19 , wherein the selected operation mode is the USPP mode when the selected word line is included in one of the middle word lines.
23. The read method of claim 19 , wherein the selected operation mode is the USPP mode when the selected word line is included in one of the upper word lines.
24. The read method of claim 16 , wherein the pre-pulse voltage is identical to the read pass voltage.
25. A storage device, comprising:
a nonvolatile memory device including a cell string connected to a bit line and a string selection line, the cell string including a plurality of memory cells connected in series, the plurality of memory cells being connected to a plurality of word lines, respectively and stacked in a direction perpendicular to a substrate; and
a memory controller configured to control the nonvolatile memory device,
the nonvolatile memory device being configured to provide a pre-pulse voltage to a selected word line or the string selection line before sensing memory cells during a read operation or a program verify operation.
26. The storage device of claim 25 , wherein the memory controller is configured to control the read operation or configured to control the program verify operation such that their operation modes for providing the pre-pulse voltage are different from each other.
27. The storage device of claim 25 , wherein the nonvolatile memory device is configured to perform the read operation or the program verify operation such that their operation modes for providing the pre-pulse voltage are different from each other.
28. The storage device of claim 27 , wherein the nonvolatile memory device is configured to determine a location of a selected word line, to select one of the plurality of operation modes for providing the pre-pulse voltage according to the location of the selected word line, and to perform the read operation or to perform the program verify operation according to the selected operation mode.
29. The storage device of claim 25 , wherein the read operation includes provided the pre-pulse voltage to the string selection line before sensing memory cells.
30. The storage device of claim 25 , wherein
the program verify operation includes providing the pre-pulse voltage to the string selection line when the selected word line is included in one of upper word lines adjacent to the string select line, and
the program verify operation includes providing the pre-pulse voltage to the selected word line when the selected word line is included in one of lower word lines adjacent to a common source line.