Resistance sensing and compensation for non-volatile storage

• US 7,590,002 B2
• Filed: 12/29/2006
• Issued: 09/15/2009
• Est. Priority Date: 12/29/2006
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Cernea, Raul-Adrian, Mokhlesi, Nima
• Primary Examiner(s): Hoang; Huan
• Application Number:
  US11/617,972
• Publication Number:
  US 20080158967A1
• Time in Patent Office: 991 Days
• Field of Search: 365/185.17, 365/185.18, 365/185.02
• US Class Current: 365/185.17
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/28 using differential sensing or reference cells, e.g. dummy cells
• CPC Class Codes: G11C 2211/5634 Reference cells

Abstract

When reading data from a non-volatile storage element that is part of a group of connected non-volatile storage elements, resistance information is measured for the group. One or more read parameters are set based on the measured resistance information. The read process is then performed using the one or more parameters.

Claims

1. A method for reading data from non-volatile storage, comprising:

measuring resistance information for a group of connected non-volatile storage elements;

choosing a read parameter in response to and based on the resistance information; and

reading data from a non-volatile storage element of said group of connected non-volatile storage elements using said resistance information, including performing a read operation using the read parameter.

2. A method according to claim 1, wherein:

said measuring resistance information includes classifying said group as pertaining to a high resistance state or a low resistance state; and

said reading data includes choosing a read parameter based on whether said group has been classified as pertaining to said high resistance state or said low resistance state, said reading data using said resistance information includes performing a read operation using said read parameter.

3. A method according to claim 1, wherein:

said reading data includes choosing a bit line voltage for said group based on said resistance information.

4. A method according to claim 1, wherein:

said reading data includes choosing a control gate voltage for .said non-volatile storage element based on said resistance information.

5. A method according to claim 1, wherein:

said reading data includes choosing a time period for testing said non-volatile storage element.

6. A method according to claim 1, wherein:

said reading data includes choosing a reference signal for testing current flow for said non-volatile storage element.

7. A method according to claim 1, wherein:

said reading data includes providing compensation to a neighbor storage element of said non-volatile storage element while sensing from said non-volatile storage element.

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

determining condition information for said neighbor storage element, said condition information indicates a condition of said neighbor storage element; and

adjusting said condition information if said resistance information indicates a first resistance condition for said group, said compensation is based on said condition information.

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

reporting said data.

10. A method according to claim 1, wherein:

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

11. A method according to claim 10, wherein:

said measuring resistance information includes applying a first voltage to a first subset of said group of connected non-volatile storage elements and applying a second voltage to a second subset of said group of connected non-volatile storage elements;

said first subset includes said non-volatile storage element and other storage elements on said NAND string that are on a first side of said non-volatile storage element; and

said second subset includes other storage elements on said NAND string that are on a second side of said non-volatile storage element.

12. A method according to claim 11, wherein:

said group of connected non-volatile storage elements stores multiple bits of data in each non-volatile storage element of said group; and

said resistance information is indicative of resistance of a portion of said NAND string.

13. A method for reading data from non-volatile storage, comprising:

measuring resistance information for a plurality of NAND strings, each of said NAND strings includes a set of non-volatile storage elements;

separately choosing a parameter value for each NAND string based on said resistance information; and

performing one or more read operations on at least one non-volatile storage element for each NAND string using said parameter.

14. A method according to claim 13, wherein:

said parameter value is a bit line voltage.

15. A method according to claim 13, wherein:

said parameter value is a word line voltage.

16. A method according to claim 13, wherein:

said performing one or more read operations uses a sense amplifier; and

said parameter value is provided to said sense amplifier.

17. A method according to claim 13, wherein:

each NAND string includes a target non-volatile storage element and a neighbor non-volatile storage element next to said target non-volatile storage element, said one or more read operations are performed on said target non-volatile storage element and include providing compensation to said neighbor non-volatile storage element while reading from said target non-volatile storage element;

said method further comprises determining condition information for said neighbor storage element, said condition information indicates a condition of said neighbor storage element; and

said method further comprises adjusting said condition information if said resistance information indicates a first resistance condition for a respective NAND string, said compensation is based on said condition information.

18. A method according to claim 13, wherein:

said measuring resistance information includes applying a first bit line voltage to said plurality of NAND strings;

said performing one or more read operations includes applying a second bit line voltage to said plurality of NAND strings; and

said second bit line voltage is greater than said first bit line voltage.

19. A method according to claim 13, wherein:

said measuring resistance information includes using a first integration time for said plurality of NAND strings;

said performing one or more read operations includes using a second integration time for said plurality of NAND strings; and

said second integration time is longer than said first integration time.

20. A method for reading data from non-volatile storage, comprising:

measuring resistance information for a group of connected non-volatile storage elements, said group of connected non-volatile storage elements includes a target non-volatile storage element and a neighbor non-volatile storage element that is next to said target non-volatile storage element;

determining condition information for said neighbor non-volatile storage element, said condition information is indicative of a condition of said neighbor non-volatile storage element; and

performing one or more read operations for said target non-volatile storage element while providing compensation to said neighbor non-volatile storage element, said compensation is based on said condition information and said resistance information.

21. A method according to claim 20, wherein:

said condition information indicates a data state of said neighbor non-volatile storage element.

22. A method according to claim 20, wherein:

said group of connected non-volatile storage elements is a NAND string; and

said resistance information is indicative of resistance of a portion of said NAND string.

23. A method of sensing resistance information for non-volatile storage, comprising:

applying a first voltage to a first subset of non-volatile storage elements on a NAND string;

applying a second voltage to a second subset of non-volatile storage elements on said NAND string; and

sensing resistance information for said NAND string based on a current flowing in said NAND string in response to applying said first voltage and said second voltage.

24. A method according to claim 23, wherein:

said steps of applying said first voltage and applying said second voltage are part of a process that reads data from a target non-volatile storage element on said NAND string;

said first subset of non-volatile storage elements includes said target non-volatile storage element and other non-volatile storage elements of said NAND string on a first side of said target non-volatile storage element; and

said second subset of non-volatile storage elements includes non-volatile storage elements of said NAND string on a second side of said target non-volatile storage element.

25. A method according to claim 24, wherein:

said first voltage is applied to a control gate for said first subset of non-volatile storage elements; and

said second voltage is applied to a control gate for said second subset of non-volatile storage elements.