Nonvolatile memory device, storage device including nonvolatile memory device and reading method of nonvolatile memory device
A nonvolatile memory device includes a memory cell array and a row decoder circuit. The row decoder circuit turns on memory cells of a plurality of cell strings of a selected memory block after applying a first prepulse to a first dummy word line connected to first dummy memory cells after applying a second prepulse to a second dummy word line connected to second dummy memory cells.
1. A nonvolatile memory device, comprising:
at least one memory block, including at least a first memory block comprising a plurality of cell strings arranged in rows and columns stacked perpendicular to a substrate, wherein the cell strings include: string select transistors (SSTs) connected to string select lines (SSLs), ground select transistors (GSTs) connected to ground select lines (GSLs), a plurality of nonvolatile memory cells connected to word lines, and first and second dummy memory cells connected to first and second dummy word lines; and
a row decoder circuit configured to apply voltage waveforms to the SSLs, GSLs, word lines, and first and second dummy word lines during a data read operation, including:
applying a string line select voltage to a selected SSL for selected cell strings to turn on the SSTs of the selected cell strings,
applying a ground line select voltage to a selected GSL for selected cell strings to turn on the GSTs of the selected cell strings,
applying a read pass voltage to unselected word lines of unselected nonvolatile memory cells to turn on the unselected nonvolatile memory cells of the selected cell strings,
applying a read select voltage to a selected word line of selected nonvolatile memory cells to read data from the selected nonvolatile memory cells,
applying a SSL prepulse to SSLs of unselected cell strings, and then applying an unselected SSL voltage to turn off the SSTs of the unselected cell strings;
applying a GSL prepulse to GSLs of unselected cell strings, and then applying an unselected GSL voltage to turn off the GSTs of the unselected cell strings;
applying a first dummy word line prepulse to the first dummy word line such that the first dummy memory cells are turned on and then turned off, and subsequently applying a first dummy word line voltage to the first dummy word line to turn on the first dummy cells again; and
applying a second dummy word line prepulse to the second dummy word line such that the second dummy memory cells are turned on and then turned off, and subsequently applying a second dummy word line voltage to the second dummy word line to turn on the second dummy cells again.
2. The nonvolatile memory device of claim 1 , wherein the first dummy word line prepulse and second dummy word line prepulse are applied such that the first and second dummy cells are turned off at approximately a same time as each other.
3. The nonvolatile memory device of claim 2 , wherein the first dummy word line prepulse and second dummy word line prepulse are applied prior to an end of the SSL prepulse and an end of the GSL prepulse.
4. The nonvolatile memory device of claim 1 , wherein the first dummy memory cell is disposed adjacent to the GST and the second dummy memory cell is disposed adjacent to the SST.
5. The nonvolatile memory device of claim 4 , further comprising:
a voltage generator;
a first dummy word line pass transistor connected between the voltage generator and the first dummy word line to apply the first dummy word line prepulse to the first dummy word line in response to a first dummy word line pass transistor control pulse applied to a control terminal of the first dummy word line pass transistor; and
a second dummy word line pass transistor connected between the voltage generator and the second dummy word line to apply the second dummy word line prepulse to the second dummy word line in response to a second dummy word line pass transistor control pulse applied to a control terminal of the second dummy word line pass transistor,
wherein a duration of the second dummy word line pass transistor control pulse is less than a duration of the first dummy word line pass transistor control pulse.
6. The nonvolatile memory device of claim 5 , wherein the second dummy word line pass transistor control pulse ends prior to a time when the first dummy word line pass transistor control pulse ends, and wherein a recovery time of the second dummy word line prepulse is greater than a recovery time of the first dummy word line prepulse.
7. The nonvolatile memory device of claim 6 , wherein the first dummy word line pass transistor control pulse and the second dummy word line pass transistor control pulse start at approximately a same time as each other.
8. The nonvolatile memory device of claim 6 , wherein the recovery time of the second dummy word line prepulse decreases as temperature increases.
9. The nonvolatile memory device of claim 6 , wherein a magnitude of the second dummy word line prepulse decreases as temperature increases.
10. The nonvolatile memory device of claim 6 , wherein the recovery time of the second dummy word line prepulse increases as the read pass voltage increases.
11. The nonvolatile memory device of claim 6 , wherein a magnitude of the second dummy word line prepulse increases as the read pass voltage increases.
12. The nonvolatile memory device of claim 5 , wherein at least one of the cell strings comprises a pillar that extends in a direction perpendicular to the substrate, wherein a diameter of the pillar is greater at an end furthest from the substrate than at an end closest to the substrate.
13. The nonvolatile memory device of claim 1 , wherein the first dummy word line voltage is less than the unselected SSL voltage which in turn is less than or equal to the unselected GSL voltage which is in turn less than or equal to the read pass voltage.
14. The nonvolatile memory device of claim 1 , wherein a duration of the first dummy word line prepulse and a duration of the second dummy word line prepulse are each less than a duration of the SSL and a duration of the GSL prepulse.
15. A nonvolatile memory device, comprising:
at least one memory block, including at least a first memory block comprising a plurality of cell strings arranged in rows and columns stacked perpendicular to a substrate, wherein the cell strings include: SSTs connected to string select lines (SSLs), ground select transistors (GSTs) connected to ground select lines (GSLs), a plurality of nonvolatile memory cells connected to word lines, and first and second dummy memory cells connected to first and second dummy word lines; and
a row decoder circuit configured to apply voltage waveforms to the SSLs, GSLs, word lines, and first and second dummy word line during a data read operation, including:
applying a string line select voltage to a selected SSL for selected cell strings to turn on the SSTs of the selected cell strings,
applying a ground line select voltage to a selected GSL for selected cell strings to turn on the GSTs of the selected cell strings,
applying a read pass voltage to unselected word lines of unselected nonvolatile memory cells to turn on the unselected nonvolatile memory cells of the selected cell strings,
applying a read select voltage to a selected word line of selected nonvolatile memory cells to read data from the selected nonvolatile memory cells,
applying a SSL prepulse to SSLs of unselected cell strings, and then applying an unselected SSL voltage to turn off the SSTs of the unselected cell strings;
applying a GSL prepulse to GSLs of unselected cell strings, and then applying an unselected GSL voltage to turn off the GSTs of the unselected cell strings;
applying a first dummy word line prepulse to the first dummy word line such that the first dummy memory cells are turned on and then turned off, and subsequently applying a first dummy word line voltage to the first dummy word line to turn on the first dummy cells again; and
applying a second dummy word line prepulse to the second dummy word line such that the second dummy memory cells are turned on and then turned off, and subsequently applying a first dummy word line voltage to the first dummy word line to turn on the first dummy cells again,
wherein the row decoder circuit is further configured to apply positive recovery voltages to the word lines and first and second dummy word lines at an end of the data read operation.
16. A method of performing a data operation for a nonvolatile memory device comprising: at least one memory block, the memory block comprising a plurality of cell strings arranged in rows and columns stacked perpendicular to a substrate, wherein the cell strings include: string select transistors (SSTs) connected to string select lines (SSLs), ground select transistors (GSTs) connected to ground select lines (GSLs), a plurality of nonvolatile memory cells connected to word lines, and first and second dummy memory cells connected to first and second dummy word lines, the method comprising:
applying a string line select voltage to a selected SSL for selected cell strings to turn on the SSTs of the selected cell strings;
applying a ground line select voltage to a selected GSL for selected cell strings to turn on the GSTs of the selected cell strings;
applying a read pass voltage to unselected word lines of unselected nonvolatile memory cells to turn on the unselected nonvolatile memory cells of the selected cell strings;
applying a read select voltage to a selected word line of selected nonvolatile memory cells to read data from the selected nonvolatile memory cells;
applying a SSL prepulse to SSLs of unselected cell strings, and then applying an unselected SSL voltage to turn off the SSTs of the unselected cell strings;
applying a GSL prepulse to GSLs of unselected cell strings, and then applying an unselected GSL voltage to turn off the GSTs of the unselected cell strings;
applying a first dummy word line prepulse to the first dummy word line such that the first dummy memory cells are turned on, then turned off, and subsequently applying a first dummy word line voltage to the first dummy word line to turn on the first dummy cells again; and
applying a second dummy word line prepulse to the second dummy word line such that the second dummy memory cells are turned on and then turned off, and subsequently applying a first dummy word line voltage to the first dummy word line to turn on the first dummy cells again.
17. The method of claim 16 , wherein the first dummy word line prepulse and second dummy word line prepulse are applied such that the first and second dummy cells are turned off at approximately a same time as each other.
18. The method of claim 17 , wherein the first dummy word line prepulse and second dummy word line prepulse are applied prior to an end of the SSL prepulse and an end of the GSL prepulse.
19. The method of claim 17 , wherein the first dummy memory cell is disposed adjacent to the GST and the second dummy memory cell is disposed adjacent to the SST, and wherein the nonvolatile memory device further comprises: a voltage generator; a first dummy word line pass transistor connected between the voltage generator and the first dummy word line; and a second dummy word line pass transistor connected between the voltage generator and the second dummy word line, the method further comprising:
applying a first dummy word line pass transistor control pulse to a control terminal of the first dummy word line pass transistor to apply the first dummy word line prepulse to the first dummy word line; and
applying a second dummy word line pass transistor control pulse to a control terminal of the second dummy word line pass transistor to apply the second dummy word line prepulse to the second dummy word line,
wherein a duration of the second dummy word line pass transistor control pulse is less than a duration of the first dummy word line pass transistor control pulse.
20. The method of claim 19 , further comprising ending the second dummy word line pass transistor control pulse prior ending the first dummy word line pass transistor control pulse, and wherein a recovery time of the second dummy word line prepulse is greater than a recovery time of the first dummy word line prepulse.