System for operating non-volatile memory using temperature compensation of voltages of unselected word lines and select gates

• US 7,342,831 B2
• Filed: 06/16/2006
• Issued: 03/11/2008
• 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:
  US11/424,812
• Publication Number:
  US 20070291567A1
• Time in Patent Office: 634 Days
• Field of Search: 365/185.17, 365/185.18, 365/185.2, 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 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 control lines, the one or more circuits (a) applying at least a first voltage to a selected control line to determine a programming condition of at least the first non-volatile storage element which is associated with the selected control line, the at least the first non-volatile storage element being provided in the set of non-volatile storage elements, and (b) applying a temperature-compensated voltage to at least a first unselected control line which is associated with the set of non-volatile storage elements, during at least a portion of a time in which the at least the first voltage is applied.

2. The non-volatile storage system of claim 1, wherein:

the one or more circuits apply a series of the first voltages to the selected control line to determine the programming condition of the at least the first non-volatile storage element, the temperature-compensated voltage being applied when each first voltage in the series of first voltages is applied to the selected control line.

3. The non-volatile storage system of claim 1, wherein:

a level of the temperature-compensated voltage is set based on a relative position of the at least the first unselected control line among the plurality of control lines.

4. The non-volatile storage system of claim 1, wherein:

the one or more circuits apply a voltage which is not temperature-compensated, or is temperature-compensated by a reduced amount relative to the temperature-compensated voltage applied to the first unselected control line, to a second unselected control line which directly neighbors the selected control line, during at least the portion of the time in which the at least the first voltage is applied.

5. The non-volatile storage system of claim 1, wherein:

the one or more circuits apply a temperature-compensated voltage to a control gate of at least one select gate of a NAND string which includes the at least the first non-volatile storage element, during at least the portion of the time in which the at least the first voltage is applied.

6. The non-volatile storage system of claim 1, wherein:

the temperature-compensated voltage is sufficient to maintain non-volatile storage elements associated with the at least the first unselected control line in a conducting state.

7. The non-volatile storage system of claim 1, wherein:

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

8. The non-volatile storage system of claim 1, wherein:

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

9. The non-volatile storage system of claim 1, wherein:

the at least the first voltage is temperature-compensated.

10. The non-volatile storage system of claim 1, wherein:

the at least the first voltage is temperature-compensated based on a relative position of the selected control line among the plurality of control lines.

11. The non-volatile storage system of claim 1, wherein:

the set of non-volatile storage elements comprises multi-level storage elements.