Flash memory device employing disturbance monitoring scheme

• US 7,554,847 B2
• Filed: 03/30/2007
• Issued: 06/30/2009
• Est. Priority Date: 08/28/2006
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Jong-Soo
• Primary Examiner(s): Dinh; Son
• Assistant Examiner(s): REIDLINGER, RONALD LANCE
• Application Number:
  US11/730,291
• Publication Number:
  US 20080049507A1
• Time in Patent Office: 823 Days
• Field of Search: 365/185.17, 365/200, 365/201, 365/185.28, 365/185.11, 365/185.18, 365/189.05, 365/185.23, 365/230.08, 365/238.5
• US Class Current: 365/185.18
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/3418 Disturbance prevention or evaluation; Refreshing of disturbed memory data
• CPC Class Codes: G11C 7/02 with means for avoiding parasitic signals
• CPC Class Codes: G11C 7/18 Bit line organisation; Bit line lay-out

Abstract

A flash memory device comprises a memory cell array including a plurality of NAND strings respectively connected to a plurality of bit lines, and further comprising a disturbed string coupled to a disturbed bit line. In a program operation of the flash memory device, a voltage level of the disturbed bit line is detected to detect program or pass voltage disturbance in the memory cell array.

Claims

1. A flash memory device, comprising:

a memory cell array comprising a plurality of NAND strings respectively connected to a plurality of bit lines, and further comprising first and second disturbed strings respectively coupled to first and second disturbed bit lines, wherein each of the plurality of NAND strings comprises a plurality of memory cells and each of the first and second disturbed strings comprises a plurality of memory cells;

a row selector adapted to drive word lines respectively connected to the plurality of memory cells within each of the plurality of NAND strings and within the first disturbed string;

a page buffer circuit electrically connected to the bit lines and the first and second disturbed bit lines;

a bias circuit configured to drive a common gate line connected to the memory cells in the second disturbed string; and

a controller configured to control operation of the row selector, the page buffer circuit, and the bias circuit;

wherein during a program operation, the controller operates to control the page buffer circuit and the bias circuit such that one or more memory cells in the first disturbed string assume states indicative of program voltage disturbance and one or more memory cells in the second disturbed string assume states indicative of pass voltage disturbance.

2. The flash memory device of claim 1, wherein during the program operation, the controller operates to control the page buffer circuit and the bias circuit to drive the first and second disturbed bit lines with a power source voltage and a ground voltage, respectively, and to drive the common gate line with a pass voltage.

3. The flash memory device of claim 1, wherein a verify-read operation for the first and second disturbed strings is performed subsequent to the program operation for the NAND strings.

4. The flash memory device of claim 3, wherein during the verify-read operation, the controller controls the row selector and the bias circuit to drive the word lines and the common gate line with a ground voltage.

5. The flash memory device of claim 4, wherein during the verify-read operation, the page buffer circuit detects voltages apparent on the first and second disturbed bit lines and stores results of the detection in a disturbed state register within the controller.

6. The flash memory device of claim 5, wherein the controller outputs the results of the detection stored in the disturbed state register to an external system, together with results of the program operation, in response to a state read command.

7. The flash memory device of claim 5, wherein the disturbed state register outputs the results of the detection to an external system in response to a disturbed state read command.

8. The flash memory device of claim 1, wherein a verify-read operation for the first and second disturbed strings is carried out in response to a disturbed verify-read command provided from an external source after the program operation.

9. The flash memory device of claim 8, wherein during the verify-read operation, the controller controls the row selector and the bias circuit to drive the word lines and the common gate line with a ground voltage.

10. The flash memory device of claim 9, wherein during the verify-read operation, the page buffer circuit detects voltages apparent on the first and second disturbed bit lines and stores results of the detection in a disturbed state register in the controller.

11. The flash memory device of claim 10, wherein the controller outputs the results of the detection stored in the disturbed state register to an external system in response to a state read command.

12. The flash memory device of claim 1, wherein each of the NAND strings and the first and second disturbed strings comprises a string select transistor and a ground select transistor respectively connected to a string select line and a ground select line driven by the row selector.

13. A flash memory device comprising:

a memory cell array including a plurality of NAND strings respectively connected to a plurality of bit lines and a disturbed string connected to a disturbed bit line, wherein each of the plurality of NAND strings comprises a plurality of memory cells and the disturbed string comprises a plurality of memory cells;

a row selector adapted to drive word lines respectively connected to the plurality of memory cells within each of the plurality of NAND strings and within the disturbed string;

a page buffer circuit electrically connected to the bit lines and the disturbed bit line; and

a controller configured to control operation of the row selector and the page buffer circuit;

wherein during every program operation of the plurality of NAND strings, the controller controls the page buffer circuit to drive the disturbed bit line with a power source voltage.

14. The flash memory device of claim 13, wherein a verify-read operation for the disturbed string is performed subsequent to the program operation.

15. The flash memory device of claim 14, wherein during the verify-read operation, the controller controls the row selector to drive the word lines with a ground voltage.

16. The flash memory device of claim 15, wherein during the verify-read operation, the page buffer circuit detects a voltage apparent on the disturbed bit line and stores a result of the detection in a disturbed state register within the controller.

17. The flash memory device of claim 16, wherein the controller outputs the result of the detection from the disturbed state register to an external system, together with results of the program operation, in response to a state read command.

18. The flash memory device of claim 16, wherein the controller outputs the result of the detection from the disturbed state register to an external system in response to a state read command.

19. The flash memory device of claim 13, wherein a verity-read operation for the disturbed string is carried out in response to a disturbed verify-read command provided from an external source after the program operation.

20. The flash memory device of claim 19, wherein during the verify-read operation, the controller controls the row selector to drive the word lines with a ground voltage.

21. The flash memory device of claim 20, wherein during the verify-read operation, the page buffer circuit detects a voltage apparent on the disturbed bit line and stores a result of the detection in a disturbed state register within the controller.

22. The flash memory device of claim 21, wherein the controller outputs the result of the detection stored in the disturbed state register to an external system in response to a state read command.

23. The flash memory device of claim 13, wherein each of the NAND strings and the disturbed string comprises a string select transistor and a ground select transistor respectively connected to a string select line and a ground select line driven by the row selector.

24. A flash memory device, comprising:

a memory cell array including a plurality of NAND strings respectively connected to a plurality of bit lines and a disturbed string connected to a disturbed bit line, wherein each of the plurality of NAND strings comprises a plurality of memory cells and the disturbed string comprises a plurality of memory cells;

a row selector adapted to drive word lines respectively connected to the plurality of memory cells within each of the plurality of NAND strings;

a page buffer circuit electrically connected to the bit lines and the disturbed bit line;

a bias circuit configured to drive a common gate line connected to the memory cells in the disturbed string; and

a controller configured to control operation of the row selector and the page buffer circuit;

wherein during a program operation, the controller controls the page buffer circuit and the bias circuit such that one or more memory cells in the disturbed string assume states indicative of pass voltage disturbance.

25. The flash memory device of claim 24, wherein during the program operation, the controller operates to control the page buffer circuit and the bias circuit to drive the disturbed bit line with a ground voltage and to drive the common gate line with a pass voltage.

26. The flash memory device of claim 24, wherein a verify-read operation for the disturbed string is performed subsequent to the program operation for the NAND strings.

27. The flash memory device of claim 26, wherein during the verify-read operation, the controller controls the bias circuit to drive the common gate line with a ground voltage.

28. The flash memory device of claim 27, wherein during the verify-read operation, the page buffer circuit detects a voltage apparent on the disturbed bit line and stores a result of the detection in a disturbed state register within the controller.

29. The flash memory device of claim 28, wherein the controller outputs the result of the detection stored in the disturbed state register to an external system, together with results of the program operation, in response to a state read command.

30. The flash memory device of claim 28, wherein the disturbed state register outputs the result of the detection to an external system in response to a disturbed state read command.

31. The flash memory device of claim 24, wherein a verify-read operation for the disturbed string is carried out in response to a disturbed verify-read command provided from an external source after the program operation.

32. The flash memory device of claim 31, wherein during the verify-read operation, the controller controls the row selector and the bias circuit to drive the word lines and the common gate line with a ground voltage.

33. The flash memory device of claim 32, wherein during the verify-read operation, the page buffer circuit detects a voltage apparent on the disturbed bit line and stores a result of the detection in a disturbed state register in the controller.

34. The flash memory device of claim 33, wherein the controller outputs the results of the detection stored in the disturbed state register to an external system in response to a state read command.

35. The flash memory device of claim 24, wherein each of the NAND strings and the disturbed string comprises a string select transistor and a ground select transistor respectively connected to a string select line and a ground select line driven by the row selector.

36. A method for operating a flash memory device comprising a memory cell array comprising a plurality of NAND strings respectively connected to a plurality of bit lines, and further comprising a first disturbed string coupled to a first disturbed bit line, the method comprising:

during every program operation of the plurality of NAND strings, driving the disturbed bit line with a power source voltage; and

,

detecting a voltage level of the first disturbed bit line to detect program voltage disturbance in the memory cell array.

37. The method of claim 36, wherein the memory cell array further comprises a second disturbed string coupled to a second disturbed bit line, and the method further comprises:

detecting a voltage level of the second disturbed bit line to detect pass voltage disturbance in the memory cell array.

38. A method for operating a flash memory device comprising a memory cell array comprising a plurality of NAND strings respectively connected to a plurality of bit lines, and further comprising a disturbed string comprising a plurality of memory cells, wherein the disturbed string is coupled to a disturbed bit line, the method comprising:

driving a common gate line connected to gates of the memory cells in the disturbed string using a bias circuit; and

,

detecting a voltage level of the disturbed bit line to detect pass voltage disturbance in the memory cell array.