Verify operation for non-volatile storage using different voltages

• US 7,440,331 B2
• Filed: 06/01/2006
• Issued: 10/21/2008
• Est. Priority Date: 06/01/2006
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Hemink, Gerrit Jan
• Primary Examiner(s): LE, VU ANH
• Application Number:
  US11/421,667
• Publication Number:
  US 20070279993A1
• Time in Patent Office: 873 Days
• Field of Search: 365/185.22, 365/185.03, 365/185.17
• US Class Current: 365/185.22
• CPC Class Codes: G11C 16/3418 Disturbance prevention or evaluation; Refreshing of disturbed memory data
• CPC Class Codes: G11C 8/08 Word line control circuits, e.g. drivers, boosters, pull-up circuits, pull-down circuits, precharging circuits, for word lines
• CPC Class Codes: G11C 8/10 Decoders

Abstract

When performing a data sensing operation, including a verify operation during programming of non-volatile storage elements (or, in some cases, during a read operation after programming), a first voltage is used for unselected word lines that have been subjected to a programming operation and a second voltage is used for unselected word lines that have not been subjected to a programming operation. In some embodiments, the second voltage is lower than the first voltage.

Claims

1. A method for using non-volatile storage, comprising:

applying a particular voltage to a particular non-volatile storage element of a group of connected non-volatile storage elements;

applying a first voltage to a first set of one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes since a last relevant erase, said first voltage is applied while applying said particular voltage;

applying a second voltage to a second set of two or more non-volatile storage elements of said group that have not been subjected to a programming process since said last relevant erase, said second voltage is applied while applying said particular voltage;

sensing a condition related to said particular non-volatile storage element in response to said applying of said particular voltage, said sensing said condition is performed as part of a verify process while programming said particular non-volatile storage element; and

performing a read process for said particular non-volatile storage element after said programming, said read process is performed by applying a different voltage instead of said first voltage to one or more of said first set of one or more non-volatile storage elements or by applying a different voltage instead of said second voltage to one or more of said second set of one or more non-volatile storage elements.

2. A method according to claim 1, wherein:

said second voltage is lower than said first voltage.

3. A method according to claim 1, wherein:

said particular voltage is a verify reference voltage;

said first voltage is sufficiently high enough to turn on said one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes; and

said second voltage is lower than said first voltage.

4. A method according to claim 1, wherein:

said applying a different voltage instead of said first voltage to one or more of said first set of one or more non-volatile storage elements or applying a different voltage instead of said second voltage to one or more of said second set of one or more non-volatile storage elements comprises applying said first voltage to said first set of one or more non-volatile storage elements and said second set of one or more non-volatile storage elements.

5. A method according to claim 1, wherein:

said applying a different voltage instead of said first voltage to one or more of said first set of one or more non-volatile storage elements or applying a different voltage instead of said second voltage to one or more of said second set of one or more non-volatile storage elements comprises applying a common voltage to said first set of one or more non-volatile storage elements and said second set of one or more non-volatile storage elements.

6. A method according to claim 5, wherein:

said group of connected non-volatile storage elements are NAND flash memory devices that are part of a common NAND string.

7. A method according to claim 5, further comprising:

applying a third voltage to a non-volatile storage element that is a neighbor of said particular non-volatile storage element.

8. A method according to claim 5, wherein:

said one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes are on a source side of said particular non-volatile storage element; and

said non-volatile storage elements of said group that have not been subjected to a programming process are on a drain side of said particular non-volatile storage element.

9. A method according to claim 1, wherein:

said group of connected non-volatile storage elements are NAND flash memory devices that are part of a common NAND string.

10. A method for using non-volatile storage, comprising:

applying a particular voltage to a particular non-volatile storage element of a group of non-volatile storage elements connected in series;

applying a first voltage to one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes since a last relevant erase, said first voltage is applied while applying said particular voltage, a first subset of said one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes are on a first side of said particular non-volatile storage element, a second subset of said one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes are on a second side of said particular non-volatile storage element;

applying a second voltage to two or more non-volatile storage elements of said group that have not been subjected to a programming process since said last relevant erase, said second voltage is applied while applying said particular voltage, said non-volatile storage elements of said group that have not been subjected to a programming process are on said drain side of said particular non-volatile storage element; and

sensing a condition related to said particular non-volatile storage element in response to said applying of said particular voltage.

11. A method according to claim 10, further comprising:

said first side is a source side and said second side is a drain side with respect to said particular non-volatile storage element; and

said group of non-volatile storage elements comprise a NAND string.

12. A method for using non-volatile storage, comprising:

applying a particular voltage to a particular non-volatile storage element of a group of connected non-volatile storage elements;

applying a first voltage to one or more non-volatile storage elements of said group that are on a source side of said particular non-volatile storage element, said first voltage is applied in association with applying said particular voltage;

applying a second voltage to two or more non-volatile storage elements of said group that are on a drain side of said particular non-volatile storage element, said second voltage is applied in association with applying said particular voltage;

applying a voltage different then said second voltage to one or more non-volatile storage elements of said group that are on said drain side of said particular non-volatile storage element, said applying a voltage different then said second voltage is applied in association with applying said particular voltage; and

sensing a condition related to said particular non-volatile storage element and said particular voltage.

13. A method according to claim 12, wherein:

said particular voltage is a verify reference voltage;

said first voltage is sufficiently high enough to turn on said one or more non-volatile storage elements on said source side of said particular non-volatile storage element;

said second voltage is sufficiently high enough to turn on said two or more non-volatile storage elements on said drain side of said particular non-volatile storage element;

said second voltage is lower than said first voltage; and

said sensing said condition is part of a verify operation during programming.

14. A method according to claim 13, wherein:

said group of connected non-volatile storage elements are NAND flash memory devices that are part of a common NAND string.

15. A method according to claim 13, wherein:

said applying a voltage different then said second voltage to one or more non-volatile storage elements of said group that are on said drain side of said particular non-volatile storage element comprises applying a third voltage to a non-volatile storage element that is a neighbor of said particular non-volatile storage element.

16. A method according to claim 13, further comprising:

programming said particular non-volatile storage element before said verify operation.

17. A method according to claim 12, wherein:

said particular voltage is a read reference voltage;

said first voltage is sufficiently high enough to turn on said one or more non-volatile storage elements on said source side of said particular non-volatile storage element;

said second voltage is sufficiently high enough to turn on said two or more non-volatile storage elements on said drain side of said particular non-volatile storage element;

said second voltage is lower than said first voltage; and

said sensing said condition is part of a read operation.

18. A method according to claim 12, wherein:

said method includes programming said particular non-volatile storage element;

said sensing a condition is part of a read operation that is performed after said programming of said particular non-volatile storage element but prior to completing programming for all of said group of connected non-volatile storage elements; and

said second voltage is lower than said first voltage.

19. A method according to claim 12, further comprising:

programming said two or more non-volatile storage elements of said group that are on said drain side;

performing a read process for said particular non-volatile storage element after said programming, said step of sensing a condition is performed as part of a verify process while programming said particular non-volatile storage element, said read process is performed by applying a common control gate voltage to said one or more non-volatile storage elements of said group that are on said source side and to said two or more non-volatile storage elements of said group that are on said drain side.

20. A method for using non-volatile storage, comprising:

applying a particular voltage to a particular non-volatile storage element of a group of connected non-volatile storage elements;

applying a first voltage to one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes since a last erase of said group, said first voltage is applied in coordination with said particular voltage;

applying a second voltage to one or more non-volatile storage elements of said group that have not already been subjected to a programming process since erasing said group, said second voltage is applied in coordination with said particular voltage;

applying a third voltage to a non-volatile storage element that is a neighbor of said particular non-volatile storage element, said third voltage is applied in coordination with said particular voltage; and

sensing a condition related to said particular non-volatile storage element and said particular voltage.

21. A method according to claim 20, wherein:

said second voltage is lower than said first voltage; and

said third voltage is higher than said second voltage and lower than said first voltage.

22. A method according to claim 20, wherein:

said particular voltage is a verify reference voltage;

said first voltage is sufficiently high enough to turn on said one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes;

said second voltage is sufficiently high enough to turn on said one or more non-volatile storage elements of said group that have not already been subjected to a programming process;

said third voltage is sufficiently high enough to turn on said neighbor;

said second voltage is lower than said first voltage; and

said sensing a condition is part of a verify operation during programming.

23. A method according to claim 20, wherein:

said particular voltage is a read reference voltage;

said first voltage is sufficiently high enough to turn on said one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes;

said second voltage is sufficiently high enough to turn on said one or more non-volatile storage elements of said group that have not already been subjected to a programming process;

said third voltage is sufficiently high enough to turn on said neighbor;

said second voltage is lower than said first voltage; and

said sensing a condition is part of a read operation.

24. A method according to claim 20, wherein:

said group of connected non-volatile storage elements are NAND flash memory devices that are part of a common NAND string.

25. A method according to claim 20, wherein:

said one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes are on a source side of said particular non-volatile storage element;

said one or more non-volatile storage elements of said group that have not already been subjected to a programming process are on a drain side of said particular non-volatile storage element; and

said non-volatile storage element that is said neighbor of said particular non-volatile storage element is on said drain side of said particular non-volatile storage element.

26. A method for using non-volatile storage, comprising:

applying a particular voltage to a particular non-volatile storage element of a group of connected non-volatile storage elements;

applying a first voltage to one or more non-volatile storage elements of said group that are on a source side of said particular non-volatile storage element;

applying a second voltage to a first set of one or more non-volatile storage elements of said group that are on a drain side of said particular non-volatile storage element;

applying said first voltage to a second set of one or more non-volatile storage elements of said group that are on said drain side of said particular non-volatile storage element; and

sensing a condition related to said particular non-volatile storage element as part of a read operation that includes said applying of said first voltage, said second voltage and said particular voltage.

27. A method according to claim 26, wherein:

one of said second set of one or more non-volatile storage elements is next to said particular non-volatile storage element.

28. A method according to claim 26, wherein:

said second voltage is lower than said first voltage.

29. A method according to claim 26, further comprising:

programming said particular non-volatile storage element prior to said sensing said condition;

programming said one or more non-volatile storage elements of said group that are on said source side of said particular non-volatile storage element prior to said sensing said condition;

programming said second set of one or more non-volatile storage elements prior to said sensing said condition, said first set of one or more non-volatile storage elements are not programmed prior to said sensing said condition.

30. A method according to claim 29, wherein:

said group of connected non-volatile storage elements are NAND flash memory devices that are part of a common NAND string.