Source side self boosting technique for non-volatile memory

• US 6,975,537 B2
• Filed: 02/03/2005
• Issued: 12/13/2005
• Est. Priority Date: 03/05/2003
• Status: Expired due to Fees

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Lutze, Jeffrey W., Chen, Jian, Higashitani, Masaaki, Li, Yan
• Primary Examiner(s): AUDUONG, GENE NGHIA
• Application Number:
  US11/049,802
• Publication Number:
  US 20050128810A1
• Time in Patent Office: 313 Days
• Field of Search: 365/185.28, 365/185.17, 365/196, 365/185.18, 365/185.22, 365/185.24, 365/185.29, 365/185.03, 365/238.5, 365/195
• US Class Current: 365/185.18
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• 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 16/3418 Disturbance prevention or evaluation; Refreshing of disturbed memory data
• CPC Class Codes: G11C 16/3454 Arrangements for verifying correct programming or for detecting overprogrammed cells

Abstract

A non-volatile semiconductor memory system (or other type of memory system) is programmed in a manner that avoids program disturb. In one embodiment that includes a flash memory system using a NAND architecture, program disturb is avoided by increasing the channel potential of the source side of the NAND string during the programming process. One exemplar implementation includes applying a voltage (e.g. Vdd) to the source contact and turning on the source side select transistor for the NAND sting corresponding to the cell being inhibited. Another implementation includes applying a pre-charging voltage to the unselected word lines of the NAND string corresponding to the cell being inhibited prior to applying the program voltage.

Claims

1. A method of programming a memory system, comprising:

performing first boosting of a voltage potential of a source side channel region of a first set of non-volatile storage elements which includes, a non-volatile storage element to be inhibited, the first boosting is performed prior to applying a program voltage to the non-volatile storage element to be inhibited and a non-volatile storage element selected for programming, the first boosting comprises applying a first voltage to control gates for a source side neighbor and source side non-neighbors of the non-volatile storage element to be inhibited; and

performing second boosting of the voltage potential, during the applying of the program voltage, by applying a second voltage, which is greater than the first voltage, to the source side non-neighbors.

2. The method of claim 1, further comprising:

maintaining the first set of non-volatile storage elements out of communication with a source line during the first boosting.

3. The method of claim 1, further comprising:

applying a lower voltage than the first voltage to the control gate of the source side neighbor, during the applying of the program voltage.

4. The method of claim 1, further comprising:

providing zero volts at control gates for drain side unselected non-volatile storage elements in the first set of non-volatile storage elements during the first boosting.

5. The method of claim 1, further comprising:

providing zero volts at a control gate for the non-volatile storage element to be inhibited during the first boosting.

6. A memory system, comprising:

a first set of non-volatile storage elements, which includes a non-volatile storage element selected for programming;

a second set of non-volatile storage elements, which includes a non-volatile storage element to be inhibited, a source side neighbor and source side non-neighbors of the non-volatile storage element to be inhibited; and

one or more managing circuits in communication with the non-volatile storage elements, the one or more managing circuits receive a request to program data, and, responsive to the request;

(a) perform first boosting of a voltage potential of a source side channel region of the second set of non-volatile storage elements, the first boosting is performed prior to applying a program voltage to the non-volatile storage element to be inhibited and the non-volatile storage element selected for programming, the first boosting comprises applying a first voltage to control gates for the source side neighbor and the source side non-neighbors, and (b) perform second boosting of the voltage potential, during the applying of the program voltage, by applying a second voltage, which is greater than the first voltage, to the source side non-neighbors.

7. The memory system of claim 6, wherein:

the one or more managing circuits maintain the second set of non-volatile storage elements out of communication with a source line during the first boosting.

8. The memory system of claim 6, wherein:

the one or more managing circuits apply a lower voltage than the first voltage to the control gate of the source side neighbor, during the applying of the program voltage.

9. The memory system of claim 6, further comprising:

a plurality of word lines, including drain side word lines, for providing zero volts at control gates for drain side unselected non-volatile storage elements in the first set of non-volatile storage elements during the first boosting.

10. The memory system of claim 6, wherein:

the one or more managing circuits applies zero volts on a first word line, which is connected to the non-volatile storage element selected for programming and to the non-volatile storage element to be inhibited, during the first boosting.

11. A method of programming a memory system, comprising:

performing first boosting of a voltage potential of a source side channel region of a first set of non-volatile storage elements which includes a non-volatile storage element to be inhibited, the first boosting is performed prior to applying a program voltage to the non-volatile storage element to be inhibited and a non-volatile storage element selected for programming, the first boosting comprises applying a first voltage to control gates for a source side neighbor and source side non-neighbors of the non-volatile storage element to be inhibited;

following the first boosting and preceding the applying of the program voltage, applying a lower voltage than the first voltage to the control gates for the source side non-neighbors; and

performing second boosting of the voltage potential, during the applying of the program voltage, by applying a second voltage, which is greater than the first voltage, to the source side non-neighbors.

12. The method of claim 11, further comprising:

following the first boosting and preceding the applying of the program voltage, applying the lower voltage than the first voltage to the control gate for the source side neighbor.

13. The method of claim 11, further comprising:

maintaining the first set of non-volatile storage elements out of communication with a source line during the first boosting.

14. The method of claim 11, further comprising:

providing zero volts at control gates for drain side unselected non-volatile storage elements in the first set of non-volatile storage elements during the first boosting.

15. A memory system, comprising:

a first set of non-volatile storage elements, which includes a non-volatile storage element selected for programming;

a second set of non-volatile storage elements, which includes a non-volatile storage element to be inhibited, a source side neighbor and source side non-neighbors of the non-volatile storage element to be inhibited; and

one or more managing circuits in communication with the non-volatile storage elements, the one or more managing circuits receive a request to program data, and, responsive to the request;

(a) perform first boosting of a voltage potential of a source side channel region of the second set of non-volatile storage elements, the first boosting is performed prior to applying a program voltage to the non-volatile storage element to be inhibited and the non-volatile storage element selected for programming, the first boosting comprises applying a first voltage to control gates for the source side neighbor and the source side non-neighbors, (b) following the first boosting and preceding the applying of the program voltage, apply a lower voltage than the first voltage to the control gates for the source side non-neighbors, and (c) perform second boosting of the voltage potential, during the applying of the program voltage, by applying a second voltage, which is greater than the first voltage, to the source side non-neighbors.

16. The memory system of claim 15, wherein:

following the first boosting and preceding the applying of the program voltage, the one or more managing circuits apply the lower voltage than the first voltage to the control gate for the source side neighbor.

17. The memory system of claim 15, wherein:

the one or more managing circuits maintain the second set of non-volatile storage elements out of communication with a source line during the first boosting.

18. The memory system of claim 15, further comprising:

a plurality of word lines, including drain side word lines, for providing zero volts at control gates for drain side unselected non-volatile storage elements in the second set of non-volatile storage elements during the first boosting.

19. A method of programming a memory system, comprising:

performing first boosting of a voltage potential of a source side channel region of a first set of non-volatile storage elements which includes a non-volatile storage element to be inhibited, the first boosting is performed prior to applying a program voltage to the non-volatile storage element to be inhibited and a non-volatile storage element selected for programming, the first boosting comprises applying a first voltage to control gates for source side non-neighbors of the non-volatile storage element to be inhibited, applying a lower voltage than the first voltage to a control gate of the source side neighbor, and maintaining the first set of non-volatile storage elements in communication with a source line; and

performing second boosting of the voltage potential, during the applying of the program voltage, by applying a second voltage, which is greater than the first voltage, to the source side non-neighbors, and maintaining the first set of non-volatile storage elements out of communication with the source line.

20. The method of claim 19, wherein:

the maintaining the first set of non-volatile storage elements out of communication with the source line comprises controlling a voltage provided to a source side select gate associated with the first set of non-volatile storage elements so that the source line is not electrically coupled to the first set of non-volatile storage elements.

21. The method of claim 19, wherein:

the maintaining the first set of non-volatile storage elements in communication with the source line comprises controlling a voltage provided to a source side select gate associated with the first set of non-volatile storage elements so that the source line is electrically coupled to the first set of non-volatile storage elements.

22. The method of claim 21, wherein:

the voltage which is provided to the source side select gate during the first boosting is the same as a voltage on the source line.

23. The method of claim 21, wherein:

the voltage which is provided to the source side select gate during the first boosting is higher than a voltage on the source line.

24. The method of claim 21, wherein:

the voltage which is provided to the source side select gate during the first boosting is higher than a voltage on the source line by Vts, which is a threshold voltage of the source side select gate.

25. The method of claim 19, further comprising:

providing a voltage to a control gate of a drain side select gate associated with the first set of non-volatile storage elements which is higher during the first boosting than during the second boosting.

26. The method of claim 19, further comprising:

providing a voltage to a control gate of a drain side select gate associated with the first set of non-volatile storage elements which is higher during the first boosting than during the second boosting by Vtd, which is a threshold voltage of the drain side select gate.

27. The method of claim 19, further comprising:

providing zero volts at control gates for drain side unselected non-volatile storage elements in the first set of non-volatile storage elements during the first boosting.

28. The method of claim 19, further comprising:

providing zero volts at a control gate for the non-volatile storage element to be inhibited during the first boosting.

29. A memory system, comprising:

a first set of non-volatile storage elements, which includes a non-volatile storage element selected for programming;

a second set of non-volatile storage elements, which includes a non-volatile storage element to be inhibited, a source side neighbor and source side non-neighbors of the non-volatile storage element to be inhibited; and

one or more managing circuits in communication with the non-volatile storage elements, the one or more managing circuits receive a request to program data, and, responsive to the request;

(a) perform first boosting of a voltage potential of a source side channel region of the second set of non-volatile storage elements, the first boosting is performed prior to applying a program voltage to the non-volatile storage element to be inhibited and the non-volatile storage element selected for programming, the first boosting comprises applying a first voltage to control gates for the source side non-neighbor, applying a lower voltage than the first voltage to a control gate of the source side neighbor, and maintaining the second set of non-volatile storage elements in communication with a source line, and (b) perform second boosting of the voltage potential, during the applying of the program voltage, by applying a second voltage, which is greater than the first voltage, to the source side non-neighbors, and maintaining the second set of non-volatile storage elements out of communication with the source line.

30. The memory system of claim 29, wherein:

the one or more managing circuits maintains the second set of non-volatile storage elements out of communication with the source line by controlling a voltage provided to a source side select gate associated with the second set of non-volatile storage elements so that the source line is not electrically coupled to the second set of non-volatile storage elements.

31. The memory system of claim 29, wherein:

the one or more managing circuits maintains the second set of non-volatile storage elements in communication with the source line by controlling a voltage provided to a source side select gate associated with the second set of non-volatile storage elements so that the source line is electrically coupled to the second set of non-volatile storage elements.

32. The memory system of claim 31, wherein:

the voltage which is provided to the source side select gate during the first boosting is the same as a voltage on the source line.

33. The memory system of claim 31, wherein:

the voltage which is provided to the source side select gate during the first boosting is higher than a voltage on the source line.

34. The memory system of claim 31, wherein:

the voltage which is provided to the source side select gate during the first boosting is higher than the voltage on the source line by Vts, which is a threshold voltage of the source side select gate.

35. The memory system of claim 29, wherein:

the one or more managing circuits provides a voltage to a control gate of a drain side select gate associated with the second set of non-volatile storage elements which is higher during the first boosting than during the second boosting.

36. The memory system of claim 29, wherein:

the one or more managing circuits provides a voltage to a control gate of a drain side select gate associated with the second set of non-volatile storage elements which is higher during the first boosting than during the second boosting by Vtd, which is a threshold voltage of the drain side select gate.

37. The memory system of claim 29, wherein:

the one or more managing circuits provides zero volts at control gates for drain side unselected non-volatile storage elements in the second set of non-volatile storage elements during the first boosting.

38. The memory system of claim 29, wherein:

the one or more managing circuits provides zero volts at a control gate for the non-volatile storage element to be inhibited during the first boosting.