Memory device and method for operating the same
A memory device is provided. The memory device includes channel layers, word lines, memory layers disposed between the channel layers and the word lines, and memory cells defined at cross-points of the channel layers and the word lines. The memory device is configured for performing a first operation for m times and a second operation for n times, and m is equal to or larger than n. In the first operation, a first electric field is produced in a portion of the memory layers. The word lines are configured for producing a second electric field in the second operation in the portion of the memory layers, and a field direction of the second electric field is different from a field direction of the first electric field.
1. A memory device, comprising:
a plurality of channel layers;
a plurality of word lines;
a plurality of memory layers disposed between the channel layers and the word lines; and
a plurality of memory cells defined at cross-points of the channel layers and the word lines;
wherein the memory device is configured for performing a first operation for m times and a second operation for n times, and m is equal to or larger than n, wherein in the first operation, a first electric field is produced in a portion of the memory layers, and wherein the word lines are configured for producing a second electric field in the second operation in the portion of the memory layers, and a field direction of the second electric field is different from a field direction of the first electric field,
wherein in the second operation, the second electric field is produced by a first voltage applied to one of the word lines that corresponds to the portion of the memory layers and a second voltage applied to another one of the word lines that corresponds the portion.
2. The memory device according to claim 1 , comprising:
a substrate;
a plurality of stacks disposed on the substrate and separated from each other by trenches, the stacks comprising conductive strips and dielectric strips disposed alternately, the conductive strips comprising the word lines;
the memory layers disposed on sidewalls of the stacks; and
the channel layers disposed on the memory layers.
3. The memory device according to claim 2 , further comprising:
an underlying conductive layer disposed in the substrate and under the stacks;
a mask layer disposed on the stacks;
a plurality of dielectric columns disposed in remaining spaces of the trenches;
a plurality of conductors disposed on the dielectric columns; and
a plurality of plugs disposed under the dielectric columns.
4. The memory device according to claim 2 , wherein the memory layers comprises:
blocking layers disposed on the sidewalls of the stacks;
charge trapping layers disposed on the blocking layers; and
tunneling layers disposed on the charge trapping layers;
wherein the channel layers are disposed on the tunneling layers; and
wherein the first electric field and the second electric field are produced in the charge trapping layers.
5. The memory device according to claim 1 , wherein the first voltage is 1 V to 3 V, and the second voltage is 7 V to 10 V.
6. The memory device according to claim 1 , wherein in the first operation, the first electric field is produced by the first voltage applied to a first word line of a pair of word lines and the second voltage applied to a second word line of the pair of word lines, and wherein in the second operation, the second electric field is produced by the second voltage applied to the first word line and the first voltage applied to the second word line.
7. The memory device according to claim 1 , wherein in the second operation, the second electric field is produced by the first voltage or first voltages applied to the word lines that are located at one side corresponding to the portion of the memory layers and the second voltage or second voltages applied to the word lines that are located at another side corresponding to the portion.
8. The memory device according to claim 7 , wherein in the second operation, second electric fields are produced sequentially through a corresponding memory layer comprising the portion.
9. A method for operating a memory device, wherein the memory device comprises a plurality of channel layers, a plurality of word lines, a plurality of memory layers disposed between the channel layers and the word lines, and a plurality of memory cells defined at cross-points of the channel layers and the word lines, and wherein the method comprises:
performing a first operation for m times, wherein in the first operation, a first electric field is produced in a portion of the memory layers; and
performing a second operation for n times, comprising:
producing a second electric field in the portion of the memory layers using the word lines, wherein a field direction of the second electric field different from a field direction of the first electric field;
wherein m is equal to or larger than n,
wherein in the second operation, the second electric field is produced by applying a first voltage to one of the word lines that corresponds to the portion of the memory layers and applying a second voltage to another one of the word lines that corresponds the portion.
10. The method according to claim 9 , wherein the field direction of the second electric field is opposite to the field direction of the first electric field.
11. The method according to claim 9 , wherein the first voltage is 1 V to 3 V, and the second voltage is 7 V to 10 V.
12. The method according to claim 9 , wherein in the first operation, the first electric field is produced by the first voltage applied to a first word line of a pair of word lines and the second voltage applied to a second word line of the pair of word lines, and wherein in the second operation, the second electric field is produced by applying the second voltage to the first word line and applying the first voltage to the second word line.
13. The method according to claim 9 , wherein in the first operation, first electric fields are produced by first voltages applied to first word lines of pairs of word lines and second voltages applied to second word lines of the pairs of word lines, and wherein in the second operation, second electric fields are produced by applying the second voltages to the first word lines and applying the first voltages to the second word lines.
14. The method according to claim 9 , wherein in the second operation, the second electric field is produced by applying the first voltage or first voltages to the word lines that are located at one side corresponding to the portion of the memory layers and applying the second voltage or second voltages to the word lines that are located at another side corresponding to the portion.
15. The method according to claim 14 , wherein in the second operation, second electric fields are produced sequentially through a corresponding memory layer comprising the portion.
16. The method according to claim 14 , wherein the second voltages are pass through voltages.
17. The method according to claim 9 , wherein a string of the memory cells corresponding to the portion of the memory layers corresponds to a 0 th word line to a m th word line, an i th word line and an (i+1) th word line correspond to the portion of the memory layers, and i is an integer equal to or larger than 0 and smaller than m, and wherein in the second operation, the second electric field is produced by applying first voltages to the (i+1) th word line to the m th word line and applying second voltages to the 0 th word line to the i th word line.
18. The method according to claim 9 , wherein a string of the memory cells corresponding to the portion of the memory layers corresponds to a 0 th word line to a m th word line, an i th word line and an (i+1) th word line correspond to the portion of the memory layers, and i is an integer equal to or larger than 0 and smaller than m, and wherein in the second operation, the second electric field is produced by applying first voltages to the 0 th word line to the i th word line and applying second voltages to the (i+1) th word line to the m th word line.