Temperature compensation of voltages of unselected word lines in non-volatile memory based on word line position

• US 7,460,407 B2
• Filed: 12/18/2007
• Issued: 12/02/2008
• Est. Priority Date: 06/16/2006
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Zhao, Dengtao, Mokhlesi, Nima
• Primary Examiner(s): Pham; Ly D
• Application Number:
  US11/958,524
• Publication Number:
  US 20080094908A1
• Time in Patent Office: 350 Days
• Field of Search: 365/185.17, 365/185.18, 365/185.21, 365/185.22, 365/185.23, 365/185.24, 365/211
• US Class Current: 365/185.22
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• 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 16/12 Programming voltage switching circuits
• CPC Class Codes: G11C 16/26 Sensing or reading circuits; Data output 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
• CPC Class Codes: G11C 2211/5621 Multilevel programming verification
• CPC Class Codes: G11C 7/04 with means for avoiding disturbances due to temperature effects

Abstract

Reading and verify operations are performed on non-volatile storage elements using temperature-compensated read voltages for unselected word lines, and/or for select gates such as drain or source side select gates of a NAND string. In one approach, while a read or verify voltage is applied to a selected word line, temperature-compensated read voltages are applied to unselected word lines and select gates. Word lines which directly neighbor the selected word line can receive a voltage which is not temperature compensated, or which is temperature-compensated to a reduced degree. The read or verify voltage applied to the selected word line can also be temperature-compensated. The temperature compensation may also account for word line position.

Claims

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

applying a voltage to a selected word line; and

during the applying, determining a programming condition of at least one non-volatile storage element which is associated with the selected word line, the at least one non-volatile storage element is provided in a set of non-volatile storage elements, and the voltage is temperature-compensated according to a relative position of the selected word line among a plurality of word lines which are associated with the set of non-volatile storage elements.

2. The method of claim 1, wherein:

a greater magnitude of temperature compensation is used when the selected word line is closer to a drain than to a source of a block which includes the plurality of word lines.

3. The method of claim 1, further comprising:

applying a series of different voltages to the selected word line to determine the programming condition of the at least one non-volatile storage element, each voltage in the series is temperature-compensated according to the relative position of the selected word line among the plurality of word lines.

4. The method of claim 1, wherein:

the voltage comprises a read voltage for reading the programming condition of the at least one non-volatile storage element after the at least one non-volatile storage element has been programmed.

5. The method of claim 1, wherein:

the voltage comprises a verify voltage for determining whether the at least one non-volatile storage element has reached a desired programming condition.

6. The method of claim 1, wherein:

the at least one non-volatile storage element is provided in a NAND string.

7. A method for operating non-volatile storage, comprising:

applying a voltage to at least one non-volatile storage element in a set of non-volatile storage element; and

during the applying, determining a programming condition of the at least one non-volatile storage element, the voltage is temperature-compensated according to a position of the at least one non-volatile storage element in the set.

8. The method of claim 7, wherein:

the non-volatile storage elements in the set are provided in a NAND string.

9. The method of claim 8, wherein:

a greater magnitude of temperature compensation is used when the at least one non-volatile storage element is closer to a drain side than to a source side of the NAND string.

10. The method of claim 7, wherein:

the determining the programming condition of the at least one non-volatile storage element comprises determining whether a threshold voltage of the at least one non-volatile storage element exceeds a specified threshold voltage.

11. A non-volatile storage system, comprising:

a set of non-volatile storage elements; and

one or more circuits in communication with the set of non-volatile storage elements via a plurality of word lines, the one or more circuits apply a voltage to a selected word line to determine a programming condition of at least one non-volatile storage element in the set of non-volatile storage elements, the voltage is temperature-compensated according to a relative position of the selected word line among the plurality of word lines.

12. The non-volatile storage system of claim 11, wherein:

a greater magnitude of temperature compensation is used when the selected word line is closer to a drain than to a source of a block which includes the plurality of word lines.

13. The non-volatile storage system of claim 11, wherein:

the one or more circuits apply a series of different voltages to the selected word line to determine the programming condition of the at least one non-volatile storage element, each voltage in the series is temperature-compensated according to the relative position of the selected word line among the plurality of word lines.

14. The non-volatile storage system of claim 11, wherein:

the voltage comprises a read voltage for reading the programming condition of the at least one non-volatile storage element after the at least one non-volatile storage element has been programmed.

15. The non-volatile storage system of claim 11, wherein:

the voltage comprises a verify voltage for determining whether the at least one non-volatile storage element has reached a desired programming condition.

16. The non-volatile storage system of claim 11, wherein:

the at least one non-volatile storage element is provided in a NAND string.

17. A non-volatile storage system, comprising:

a set of non-volatile storage elements; and

one or more circuits in communication with the set of non-volatile storage elements via a plurality of word lines, the one or more circuits;

(a) apply a voltage to at least one non-volatile storage element in the set, and (b) while applying the voltage, determine a programming condition of the at least one non-volatile storage element, the voltage is temperature-compensated according to a position of the at least one non-volatile storage element in the set.

18. The non-volatile storage system of claim 17, wherein:

the non-volatile storage elements in the set are provided in a NAND string.

19. The non-volatile storage system of claim 18, wherein:

a greater magnitude of temperature compensation is used when the at least one non-volatile storage element is closer to a drain side than to a source side of the NAND string.

20. The non-volatile storage system of claim 17, wherein:

the one or more circuits determine the programming condition of the at least one non-volatile storage element by determining whether a threshold voltage of the at least one non-volatile storage element exceeds a specified threshold voltage.