NONVOLATILE SEMICONDUCTOR MEMORY DEVICE

• US 20120195119A1
• Filed: 01/24/2012
• Published: 08/02/2012
• Est. Priority Date: 02/01/2011
• Status: Active Grant

• Current Assignee: Kioxia Corporation
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: NAGADOMI, Yasushi, TOKIWA, Naoya
• Granted Patent: US 8,582,369 B2
• Time in Patent Office: Days
• US Class Current: 365/185.03
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/10 Programming or data input circuits
• CPC Class Codes: G11C 16/3454 Arrangements for verifying correct programming or for detecting overprogrammed cells
• CPC Class Codes: G11C 16/3459 Circuits or methods to verify correct programming of nonvolatile memory cells

Abstract

In writing, a first write operation to a first memory cell is executed; and a second write operation for providing a first threshold-voltage distribution to a second memory cell adjacent to the first one, is executed. The first threshold voltage distribution is a lowest threshold-voltage distribution among the positive threshold voltage distributions. It is verified whether a desired threshold voltage distribution has been obtained in the first memory cell or not (first write verify operation), moreover, it is verified whether a first threshold voltage distribution or a threshold voltage distribution having a voltage level larger than the first threshold-voltage distribution has been obtained in the second memory cell or not (second write verify operation). A control circuit outputs results of the first write verify operation and the second write verify operation.

Claims

1. A nonvolatile semiconductor memory device, comprising:

a memory cell array including a plurality of memory cells; and

a control circuit configured to control a voltage applied to the plurality of memory cells,

the control circuit being configured to provide to the memory cells a threshold voltage distribution which is at least partly negative thereby erasing retained data of the memory cells, and to provide to the memory cells plural types of positive threshold voltage distributions thereby writing plural types of data to the memory cells,

the control circuit being configured to, in a write operation on the memory cells, execute;

a first write operation for providing plural types of positive threshold voltage distributions to a write-object first memory cell;

a first write verify operation for verifying whether the positive plural types of threshold voltage distributions have been obtained in the first memory cell or not;

a second write operation for providing a first threshold voltage distribution to a second memory cell adjacent to the first memory cell;

the first threshold voltage distribution being a lowest threshold voltage distribution among the plural types of positive threshold voltage distributions; and

a second write verify operation for verifying whether the first threshold voltage distribution or a threshold voltage distribution having a voltage level larger than the first threshold voltage distribution has been obtained in the second memory cell or not,

and output results of the first write verify operation and the second write verify operation.

2. The nonvolatile semiconductor memory device according to claim 1, wherein

the control circuit is configured to

execute the first write operation and the first write verify operation continuously on a plurality of the first memory cells that are adjacent to one another, and

execute the second write operation and the second write verify operation on the second memory cells adjacent to the plurality of first memory cells.

3. The nonvolatile semiconductor memory device according to claim 2, wherein

the second write operation and the second write verify operation are omitted in the first memory cells.

4. The nonvolatile semiconductor memory device according to claim 1, wherein

the control circuit is configured capable of, each time one memory cell of the plurality of first memory cells is selected and undergoes the first write operation and the first write verify operation, executing the second write verify operation respectively before or after the first write operation and the first write verify operation.

5. The nonvolatile semiconductor memory device according to claim 1, wherein

each of the memory cells is configured capable of storing multiple bits of data,

the multiple bits of data are supplied to the control circuit as multiple pages of data, and

the control circuit is configured to

execute the first write operation and the first write verify operation for pages of the multiple pages of data, continuously, on a page basis, on the write-object first memory cell, and

execute the second write operation and the second write verify operation on the second memory cell before and after the first write operation and the first write verify operation.

6. The nonvolatile semiconductor memory device according to claim 2, wherein

each of the memory cells is configured capable of storing multiple bits of data,

the multiple bits of data are supplied to the control circuit as multiple pages of data, and

the control circuit is configured to

execute the first write operation and the first write verify operation for one page of the multiple pages of data, on the write-object first memory cell, and

execute the second write operation and the second write verify operation on the second memory cell adjacent to the first memory cell for every first write operation and first write verify operation for the one page of data.

7. The nonvolatile semiconductor memory device according to claim 2, wherein

each of the memory cells is configured capable of storing multiple bits of data,

the multiple bits of data are supplied to the control circuit as multiple pages of data, and

the control circuit is configured to

execute the first write operation and the first write verify operation for one page of the multiple pages of data, on the write-object first memory cell, and,

when the first write operation and the first write verify operation for a first page of data are performed on the first memory cell, execute the second write operation and the second write verify operation for the second memory cell before execution of the first write operation and the first write verify operation, and,

when the first write operation and the first write verify operation for a second page of data different from the first page of data are performed on the first memory cell, omit the second write operation and the second write verify operation for the second memory cell before execution of the first write operation and the first write verify operation.

8. The nonvolatile semiconductor memory device according to claim 1, wherein

the control circuit, when a judgment result of the first write verify operation and a judgment result of the second write verify operation are both positive, judges that the write operation in the first memory cell is completed, and notifies the fact.

9. The nonvolatile semiconductor memory device according to claim 1, further comprising:

a first data register for retaining a result of the first write verify operation; and

a second data register for retaining a result of the second write verify operation.

10. The nonvolatile semiconductor memory device according to claim 9, wherein

the control circuit, when data retained in the first data register and the second data register are both a first data, judges that write of the first memory cell is completed.

11. A nonvolatile semiconductor memory device, comprising:

a memory cell array configured as an arrangement of memory strings each including a plurality of memory cells aligned in a stacking direction and connected to each other in series; and

a control circuit configured to control a voltage applied to the plurality of memory cells,

the control circuit being configured to provide to the memory cells a threshold voltage distribution which is at least partly negative thereby erasing retained data of the memory cells, and to provide to the memory cells plural types of positive threshold voltage distributions thereby writing plural types of data to the memory cells,

the control circuit being configured to, in a write operation on the memory cells, execute

a first write operation for providing plural types of positive threshold voltage distributions to a write-object first memory cell in the memory string;

a first write verify operation for verifying whether the positive plural types of threshold voltage distributions have been obtained in the first memory cell or not;

a second write operation for providing a first threshold voltage distribution to a second memory cell adjacent to the first memory cell in the memory string, the first threshold voltage distribution being a lowest threshold voltage distribution among the positive plural types of threshold voltage distributions; and

a second write verify operation for verifying whether the first threshold voltage distribution or a threshold voltage distribution having a voltage level larger than the first threshold voltage distribution has been obtained in the second memory cell or not,

and output results of the first write verify operation and the second write verify operation.

12. The nonvolatile semiconductor memory device according to claim 11, wherein

the control circuit is configured to

execute the first write operation and the first write verify operation continuously on a plurality of the first memory cells that are adjacent to one another in the memory string, and

execute the second write operation and the second write verify operation on the second memory cells adjacent to the plurality of first memory cells in the memory string.

13. The nonvolatile semiconductor memory device according to claim 12, wherein

each of the memory cells is configured capable of storing multiple bits of data,

the multiple bits of data are supplied to the control circuit as multiple pages of data, and

the control circuit is configured to

execute the first write operation and the first write verify operation for one page of the multiple pages of data, on the write-object first memory cell, and

execute the second write operation and the second write verify operation on the second memory cell adjacent to the first memory cell for every first write operation and first write verify operation for the one page of data.

14. The nonvolatile semiconductor memory device according to claim 11, wherein

the control circuit is configured capable of, each time one memory cell of the plurality of first memory cells is selected and undergoes the first write operation and the first write verify operation, executing the second write verify operation respectively before or after the first write operation and the first write verify operation.

15. The nonvolatile semiconductor memory device according to claim 11, wherein

the control circuit, when a judgment result of the first write verify operation and a judgment result of the second write verify operation are both positive, judges that the write operation in the first memory cell is completed, and notifies the fact.

16. A method of write in a nonvolatile semiconductor memory device, the nonvolatile semiconductor memory device comprising a memory cell array that includes a plurality of memory cells,

wherein each of the memory cells comprises a charge storage film for storing a charge and is configured capable of retaining plural types of threshold voltage distributions according to an amount of charge stored, and

wherein each of the memory cells is configured to be provided with a threshold voltage distribution which is at least partly negative and thereby retain data of an erased state, and to be provided with plural types of positive threshold voltage distributions and thereby be written with plural types of data,

the method comprising:

executing a first write operation for providing the plural types of positive threshold voltage distributions to a write-object first memory cell;

executing a first write verify operation for verifying whether the plural types of positive threshold voltage distributions have been obtained in the first memory cell or not;

executing a second write operation for providing a first threshold voltage distribution to a second memory cell adjacent to the first memory cell, irrespective of what kind of data is to be written to the second memory cell, the first threshold voltage distribution being a lowest threshold voltage distribution among the plural types of positive threshold voltage distributions;

executing a second write verify operation for verifying whether the first threshold voltage distribution or a threshold voltage distribution having a voltage level larger than the first threshold voltage distribution has been obtained in the second memory cell or not; and

outputting results of the first write verify operation and the second write verify operation.

17. The method of write according to claim 16, wherein

the first write operation and the first write verify operation are executed continuously on a plurality of the first memory cells that are adjacent to one another, and

the second write operation and the second write verify operation are executed on the second memory cells adjacent to the plurality of first memory cells.

18. The method of write according to claim 16, wherein

each time one memory cell of the plurality of first memory cells is selected and undergoes the first write operation and the first write verify operation, the second write verify operation is executed respectively before or after the first write operation and the first write verify operation.

19. The nonvolatile semiconductor memory device according to claim 17, further comprising:

supplying multiple bits of data for storing in one memory cell as multiple pages of data;

executing the first write operation and the first write verify operation for one page of the multiple pages of data, on the write-object first memory cell; and

executing the second write operation and the second write verify operation on the second memory cell adjacent to the first memory cell for every first write operation and first write verify operation for the one page of data.