IP Library › Granted Patent US 7,583,535
Granted Patent B2
US 7,583,535 · App. 11/618,782 · Granted Sep 1, 2009

Biasing non-volatile storage to compensate for temperature variations

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Quick Facts
Patent No.
US 7,583,535
App. No.
11/618,782
Filed
Dec 30, 2006
Granted
Sep 1, 2009
Kind
B2
Art Unit
2827
USPC
365/185.27
Abstract

A body bias is applied to a non-volatile storage system to compensate for temperature-dependent variations in threshold voltage, sub-threshold slope, depletion layer width and/or 1/f noise. A desired bias level is set based on a temperature-dependent reference signal. In one approach, a level of the biasing can decrease as temperature increases. The body bias can be applied by applying a voltage to a p-well and n-well of a substrate, applying a voltage to the p-well while grounding the n-well, or grounding the body and applying a voltage to the source and/or drain of a set of non-volatile storage elements. Further, temperature-independent and/or temperature-dependent voltages can be applied to selected and unselected word lines in the non-volatile storage system during program, read or verify operations. The temperature-dependent voltages can vary based on different temperature coefficients.

Claims (53)

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

biasing a substrate on which a set of non-volatile storage elements are formed, at least in part, the set of non-volatile storage elements is associated with a set of word lines;

during the biasing, applying a voltage to a source side of the set of non-volatile storage elements, separately from the biasing; and

during the biasing and the applying, performing a read or verify operation on at least one non-volatile storage element of the set of non-volatile storage elements, the at least one non-volatile storage element is in communication with a selected word line of the set of word lines, where the read or verify operation involves applying a temperature-independent voltage to the selected word line to determine a condition of the at least one non-volatile storage element.

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

biasing a substrate on which a set of non-volatile storage elements are formed, at least in part, the set of non-volatile storage elements is associated with a set of word lines, the biasing is set to vary with temperature to compensate at least one temperature-varying characteristic of non-volatile storage elements of the set of non-volatile storage elements;

during the biasing, applying a voltage to a source side of the set of non-volatile storage elements, separately from the biasing; and

during the biasing and the applying, performing a read or verify operation on at least one non-volatile storage element of the set of non-volatile storage elements, the at least one non-volatile storage element is in communication with a selected word line of the set of word lines.

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

biasing a substrate on which a set of non-volatile storage elements are formed, at least in part, the set of non-volatile storage elements is associated with a set of word lines;

during the biasing, applying a voltage to a source side of the set of non-volatile storage elements, separately from the biasing, and applying temperature-dependent voltages to unselected word lines of the set of word lines; and

during the biasing and the applying, performing a read or verify operation on at least one non-volatile storage element of the set of non-volatile storage elements, the at least one non-volatile storage element is in communication with a selected word line of the set of word lines.

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

biasing a substrate on which a set of non-volatile storage elements are formed, at least in part, the set of non-volatile storage elements is associated with a set of word lines;

during the biasing, applying a voltage to a source side of the set of non-volatile storage elements, separately from the biasing;

the biasing comprises applying a temperature-independent voltage to the substrate, and the voltage applied to the source side is temperature-dependent; and

during the biasing and the applying, performing a read or verify operation on at least one non-volatile storage element of the set of non-volatile storage elements, the at least one non-volatile storage element is in communication with a selected word line of the set of word lines.

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

biasing a substrate on which a set of non-volatile storage elements are formed, at least in part, the set of non-volatile storage elements is associated with a set of word lines;

during the biasing, applying a voltage to a source side of the set of non-volatile storage elements, separately from the biasing;

the biasing comprises applying a temperature-dependent voltage to the substrate, and the voltage applied to the source side is temperature-independent; and

during the biasing and the applying, performing a read or verify operation on at least one non-volatile storage element of the set of non-volatile storage elements, the at least one non-volatile storage element is in communication with a selected word line of the set of word lines.

6. The method of claim 2 , wherein:

the at least one temperature-varying characteristic comprises threshold voltage.

7. The method of claim 2 , wherein:

the at least one temperature-varying characteristic comprises a sub-threshold slope.

8. The method of claim 2 , wherein:

the at least one temperature-varying characteristic comprises depletion layer width.

9. The method of claim 2 , wherein:

the at least one temperature-varying characteristic comprises 1/f noise.

10. The method of claim 1 , wherein:

the set of non-volatile storage elements is provided in at least one NAND string which is formed, at least in part, on the substrate.

11. The method of claim 1 , wherein:

the biasing comprises applying a reverse body bias.

12. The method of claim 3 , wherein:

the temperature-dependent voltages applied to the unselected word lines vary with temperature according to a first temperature coefficient; and

the temperature-dependent biasing varies with temperature according to a second temperature coefficient which differs from the first temperature coefficient.

13. The method of claim 4 , wherein:

the substrate comprises a p-well on which the set of non-volatile storage elements is formed, at least in part, the p-well is within an n-well, and the biasing comprises applying the temperature-independent voltage to both the p-well and the n-well.

14. The method of claim 4 , wherein:

the substrate comprises a p-well on which the set of non-volatile storage elements is formed, at least in part, the p-well is within an n-well, and the biasing comprises applying the temperature-independent voltage to the p-well while grounding the n-well.

15. The method of claim 5 , wherein:

the substrate comprises a p-well on which the set of non-volatile storage elements is formed, at least in part, the p-well is within an n-well, and the biasing comprises applying the temperature-dependent voltage to both the p-well and the n-well.

16. The method of claim 5 , wherein:

the substrate comprises a p-well on which the set of non-volatile storage elements is formed, at least in part, the p-well is within an n-well, and the biasing comprises applying the temperature-dependent voltage to the p-well while grounding the n-well.

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

biasing a substrate on which a set of non-volatile storage elements are formed, at least in part, the set of non-volatile storage elements is associated with a set of word lines, where a level of the biasing decreases as temperature increases;

during the biasing, applying a voltage to a source side of the set of non-volatile storage elements, separately from the biasing; and

during the biasing and the applying, performing a read or verify operation on at least one non-volatile storage element of the set of non-volatile storage elements, the at least one non-volatile storage element is in communication with a selected word line of the set of word lines.

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

biasing a substrate on which a set of non-volatile storage elements are formed, at least in part, the set of non-volatile storage elements is associated with a set of word lines, the biasing comprises applying a forward body bias;

during the biasing, applying a voltage to a source side of the set of non-volatile storage elements, separately from the biasing; and

during the biasing and the applying, performing a read or verify operation on at least one non-volatile storage element of the set of non-volatile storage elements, the at least one non-volatile storage element is in communication with a selected word line of the set of word lines.