Program temperature dependent read

• US RE45,700 E1
• Filed: 05/21/2014
• Issued: 09/29/2015
• Est. Priority Date: 12/22/2011
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Dutta, Deepanshu
• Primary Examiner(s): Escalante, Ovidio
• Application Number:
  US14/284,193
• Time in Patent Office: 496 Days
• Field of Search: 365/185.21, 365/185.24
• US Class Current: 1/1
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 16/26 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/3459 Circuits or methods to verify correct programming of nonvolatile memory cells
• CPC Class Codes: G11C 7/04 with means for avoiding disturbances due to temperature effects

Abstract

Methods and non-volatile storage systems are provided for using compensation that depends on the temperature at which the memory cells were programmed. Note that the read level compensation may have a component that is not dependent on the memory cells'"'"' Tco. That is, the component is not necessarily based on the temperature dependence of the Vth of the memory cells. The compensation may have a component that is dependent on the difference in width of individual Vth distributions of the different states across different temperatures of program verify. This compensation may be used for both verify and read, although a different amount of compensation may be used during read than during verify.

Claims

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

verifying one or more program operations of a group of non-volatile storage elements in the non-volatile storage;

storing an indication of temperature at which the verifying was performed; and

reading the group of non-volatile storage elements using compensation that depends on the temperature at which the verifying was performed, including applying compensation that is independent of temperature dependence of the non-volatile storage elements threshold voltages.

8. The method of claim 1, wherein the reading the group of non-volatile storage elements using compensation that depends on the temperature at which the verifying was performed includes one or more of:

reading with a sensing current that depends on the temperature during the verifying;

reading with a sensing time that depends on the temperature during the verifying;

or

applying a voltage to a selected word line that depends on the temperature during the verifying.

23. The method of claim 1, wherein:

the group of non-volatile storage elements are arranged in a three-dimensional memory structure.

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

verifying one or more program operations of a group of non-volatile storage elements in the non-volatile storage, including applying different amounts of compensation to verify respective different states of a plurality of states to which the group of non-volatile storage elements are programmed, the different amounts of compensation shift a first verify level for a higher state more than a second verify level for a lower state, with increasing verify temperature;

storing an indication of temperature at which the verifying was performed; and

reading the group of non-volatile storage elements using compensation that depends on the temperature at which the verifying was performed.

3. The method of claim 2, wherein the different amounts of compensation depend at least in part on temperature dependence of threshold voltage distribution widths of the respective different states.

4. The method of claim 2, wherein the reading the group of non-volatile storage elements using compensation that depends on the temperature at which the verifying was performed includes:

applying different amounts of compensation for reading different states of the plurality of states, the different amounts of compensation shift down a first read level for the higher state more than a second read level for the lower state, with increasing temperature at which the verifying was performed.

24. The method of claim 2, wherein:

the non-volatile storage comprises a three-dimensional memory array, the three-dimensional memory array comprises the group of non-volatile storage elements.

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

verifying one or more program operations of a group of non-volatile storage elements in the non-volatile storage, including—

applying one or more first compensations for temperature dependence of the group of non-volatile storage elements threshold voltage and one or more second compensations that are independent of temperature dependence of the group of non-volatile storage elements threshold voltage;

storing an indication of temperature at which the verifying was performed; and

reading the group of non-volatile storage elements using compensation that depends on the temperature at which the verifying was performed.

6. The method of claim 5, wherein there are gaps between threshold voltage distributions that represent adjacent states of a plurality of states to which the group is programmed, the one or more second compensations decrease at least one of the gaps with increasing temperature.

7. The method of claim 5, wherein the reading the group of non-volatile storage elements using compensation that depends on the temperature at which the verifying was performed includes:

applying one or more third compensations that adjust read levels to compensate for shifts caused by the second one or more compensations.

25. The method of claim 5, wherein:

the group of non-volatile storage elements are part of a three-dimensional memory array.

9. A non-volatile storage device comprising:

a plurality of non-volatile storage elements;

a plurality of word lines, a first of the word lines is associated with a group of the plurality of non-volatile storage elements;

one or more management circuits in communication with the plurality of non-volatile storage elements and the plurality of word lines, the one or more management circuits verify one or more program operations of the group of non-volatile storage elements, the one or more management circuits store an indication of temperature at which the verify was performed, the one or more management circuits read the group of non-volatile storage elements using compensation that depends on the temperature at which the verify was performed, wherein the compensation that depends on the temperature at which the verify was performed compensates for temperature dependence of threshold voltage distribution widths of the non-volatile storage elements threshold voltages.

26. The non-volatile storage device of claim 9, wherein:

the plurality of non-volatile storage elements are arranged in a three-dimensional memory structure.

10. A non-volatile storage device comprising:

a plurality of non-volatile storage elements;

a plurality of word lines, a first of the word lines is associated with a group of the plurality of non-volatile storage elements;

one or more management circuits in communication with the plurality of non-volatile storage elements and the plurality of word lines, the one or more management circuits verify one or more program operations of the group of non-volatile storage elements, the one or more management circuits apply different amounts of compensation to verify respective different states of a plurality of states to which the group of non-volatile storage elements are programmed, the different amounts of compensation shift a first verify level for a higher state more than a second verify level for a lower state, with increasing verify temperature, the one or more management circuits store an indication of temperature at which the verify was performed, the one or more management circuits read the group of non-volatile storage elements using compensation that depends on the temperature at which the verify was performed.

11. The non-volatile storage device of claim 10, wherein the different amounts of compensation depend on threshold voltage distribution widths of the respective different states.

12. The non-volatile storage device of claim 10, wherein there are gaps between threshold voltage distributions that represent adjacent states of a plurality of states to which the group is programmed, the different amounts of compensation decrease at least one of the gaps with increasing temperature.

27. The non-volatile storage device of claim 10, wherein:

the non-volatile storage device comprises a three-dimensional memory array, the three-dimensional memory array comprises the plurality of non-volatile storage elements.

13. A method of operating non-volatile storage, comprising:

programming a group of non-volatile storage elements, the programming including performing one or more verify operations using compensation that is based on the equation;

Tco_prog1*Tprog+Tco*Tprog,

where Tprog is the temperature during program verify, Tco compensates for Vth temperature dependence of the group of non-volatile storage elements and Tco_prog1 compresses a width of a Vth distribution window of the programmed group of non-volatile storage elements with increasing temperature;

storing an indication of temperature at which the verifying was performed; and

reading the group of non-volatile storage elements using compensation that is based on the equation;

Tco_prog2*Tprog+Tco*Tread,

where Tread is the temperature during read and Tco_prog2 adjusts read levels to compensate for an effect caused by Tco_prog1 during program verify.

14. The method of claim 13, wherein the storing an indication of temperature at which the verifying was performed includes:

writing the indication to a word line that includes the group of non-volatile storage elements.

15. The method of claim 13, further comprising:

reading the indication from a selected word line when reading the group of non-volatile storage elements at a first reference level without applying compensation based on the temperature at which the verifying was performed.

16. The method of claim 13, wherein values for Tco_prog1 and Tco_prog2 are based on an erase/program cycle count for a block containing the group of non-volatile storage elements.

17. The method of claim 13, wherein the storing an indication of temperature at which the verifying was performed includes storing the indication in spare non-volatile storage elements associated with a first word line in a block, the indication of the temperature is used when reading other word lines in the block that were verified at about the same temperature.

28. The method of claim 13, wherein:

the group of non-volatile storage elements are part of a three-dimensional memory array.

18. A non-volatile storage device comprising:

a plurality of non-volatile storage elements;

a plurality of word lines, a first of the word lines is associated with a group of the plurality of non-volatile storage elements;

one or more management circuits in communication with the plurality of non-volatile storage elements and the plurality of word lines, the one or more management circuits program the group of non-volatile storage elements, the one or more management circuits perform one or more verify operations during the programming using verify reference voltages that are based on the equation;

Tco_prog1*Tprog+Tco*Tprog, where Tprog is the temperature during program verify, Tco compensates for Vth temperature dependence of the group of non-volatile storage elements and Tco_prog1 reduces gaps between states of the programmed group of non-volatile storage elements with increasing temperature, the one or more management circuits store an indication of temperature at which the verifying was performed, the one or more management circuits read the group of non-volatile storage elements using compensation that is based on the equation;

Tco_prog2*Tprog+Tco*Tread, where Tread is the temperature during read and Tco_prog2 adjusts read reference voltages to compensate for an effect to the width of the threshold voltage distribution window caused by Tco_prog1 during program verify.

29. The non-volatile storage device of claim 18, wherein:

the non-volatile storage device comprises a three-dimensional memory array, the three-dimensional memory array comprises the plurality of non-volatile storage elements.

19. A method of operating non-volatile storage, comprising:

programming a group of non-volatile storage elements to a plurality of data states at a first temperature, the programming includes verifying the plurality of data states using a first set of verify levels; and

programming the group of non-volatile storage elements to the plurality of data states at a second temperature, the programming includes verifying the plurality of data states using a second set of verify levels, the first set and the second set of verify levels compensate for temperature dependence of individual threshold distribution widths of the plurality of data states.

20. The method of claim 19, further comprising:

reading the group of non-volatile storage elements using compensation that depends on the temperature at which the group of non-volatile storage elements were programmed.

21. The method of claim 19, wherein the first set of verify levels has a first difference between verify levels for two adjacent states, the second set of verify levels has a second difference between verify levels for the two adjacent states that is less than the first difference, the second temperature is higher than the first temperature.

22. The method of claim 21, further comprising:

applying compensation for temperature dependence of threshold voltages of the group of non-volatile storage elements when verifying and reading the two adjacent states.

30. The method of claim 19, wherein:

the non-volatile storage comprises a three-dimensional memory array, the three-dimensional memory array comprises the group of non-volatile storage elements.