Probability-based remedial action for read disturb effects

• US 9,575,829 B2
• Filed: 03/13/2013
• Issued: 02/21/2017
• Est. Priority Date: 03/13/2013
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Inventors: Yang, Nian Niles, Avila, Chris, Sprouse, Steven, Manohar, Abhijeet, Huang, Yichao
• Primary Examiner(s): LAMARRE, GUY J
• Application Number:
  US13/802,140
• Publication Number:
  US 20140281766A1
• Time in Patent Office: 1,441 Days
• Field of Search: 714/721, 365/201, 365/196, 365/189.11, 365/194, 365/200, 711/106
• US Class Current: 1/1
• CPC Class Codes: G06F 11/073 in a memory management context, e.g. virtual memory or cache management memory management G06F12/00; testing of static memory units G11C29/00
• CPC Class Codes: G06F 11/0793 Remedial or corrective actions recovery from an exception in an instruction pipeline G06F9/3861; by retry G06F11/1402; for recovering from a failure of a protocol instance or entity H04L69/40
• CPC Class Codes: G11C 11/56 using storage elements with more than two stable states represented by steps, e.g. of voltage, current, phase, frequency
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/3404 Convergence or correction of memory cell threshold voltages; Repair or recovery of overerased or overprogrammed cells
• CPC Class Codes: G11C 2029/0409 Online test
• CPC Class Codes: G11C 2029/0411 Online error correction
• CPC Class Codes: G11C 29/42 using error correcting codes [ECC] or parity check
• CPC Class Codes: G11C 29/50004 of threshold voltage

Abstract

A method may be performed in a data storage device that includes a memory and a controller, in response to a request to read data from the memory. The data is located within a first word line of the memory. The method includes accessing the data from the first word line and determining, based on a probability threshold, whether to perform a remedial action with respect to a second word line.

Claims

1. A data storage device comprising:

a memory including a first word line and a second word line; and

a controller, wherein the controller is configured to access data from the first word line, to determine, based on a probability threshold, if a remedial action is to be performed with respect to the second word line, and if the remedial action is determined to be performed, to initiate the remedial action with respect to;

data stored in the second word line, and a different word line.

2. The data storage device of claim 1, wherein:

the remedial action includes scheduling the data stored in the second word line for a data move operation.

3. The data storage device of claim 1, wherein:

the remedial action includes reassigning the data stored in the second word line to the different word line.

4. The data storage device of claim 1, wherein the probability threshold is based on a read disturb threshold associated with the second word line.

5. The data storage device of claim 1, wherein:

the controller is further configured, in response to a read request, to generate a value associated with the second word line, to perform a comparison of the value to the probability threshold, and to determine, based on the comparison, whether to perform the remedial action, and

the remedial action includes reassigning the data stored in the second word line to the different word line of the memory.

6. The data storage device of claim 5, wherein the controller is configured to generate the value randomly, semi-randomly, or pseudo-randomly.

7. The data storage device of claim 6, wherein the value is selected from a range of values, wherein the probability threshold corresponds to a sub-range of the range of values, wherein the remedial action includes reassigning data stored in a third word line to a second different word line of the memory, and wherein the second word line is a neighbor of the first word line and the third word line is an edge word line of a memory block that includes the first word line and the second word line.

8. The data storage device of claim 1, wherein the controller is configured to determine a number of errors in the data stored in at least a portion of the second word line, and wherein a particular determination of whether to perform the remedial action is based on the number of errors in the data stored in the at least a portion of the second word line.

9. The data storage device of claim 1, wherein the second word line is a neighbor of the first word line, and wherein the memory includes a non-volatile memory.

10. The data storage device of claim 1, wherein the controller is configured to retrieve the data from the first word line, to decode the retrieved data to generate decoded data, and to provide the decoded data to a host device in response to a request to read the data.

11. The data storage device of claim 1, wherein the controller is configured to perform the remedial action by adding an entry corresponding to the second word line into a reassignment queue.

12. A data storage device comprising:

a memory including a first word line and a second word line; and

a controller, the controller configured to access data from the first word line, to determine based on a probability threshold if a remedial action is to be performed with respect to the second word line, the probability threshold based on a read disturb threshold associated with the second word line, and if the remedial action is determined to be performed, to initiate the remedial action with respect to;

data stored in the second word line, and a different word line.

13. The data storage device of claim 12, wherein:

the remedial action includes scheduling the data stored in the second word line for a data move operation.

14. The data storage device of claim 12, wherein the read disturb threshold is inversely proportional to a count of write/erase cycles, and wherein the controller is configured to select the probability threshold based on the count of write/erase cycles.

15. A method comprising:

in a data storage device that includes a memory and a controller, wherein the memory is configured to store data within a first word line of the memory, performing;

accessing the data from the first word line;

determining, based on a probability threshold, if a remedial action is to be performed with respect to a second word line of the memory; and

if the remedial action is determined to be performed, initiating the remedial action with respect to;

data stored in the second word line, and a different word line of the memory.

16. The method of claim 15, wherein:

the remedial action includes reassigning the data stored in the second word line to the different word line.

17. The method of claim 15, wherein determining, based on the probability threshold, if the remedial action is to be performed comprises performing a probability-based test by generating a value and comparing the value to the probability threshold, and wherein the value is generated randomly, semi-randomly, or pseudo-randomly.

18. The method of claim 15, wherein:

the probability threshold is based on a read disturb threshold associated with the second word line, and

the remedial action is performed if a generated value satisfies the probability threshold.

19. The method of claim 15, further comprising setting the probability threshold based on a read disturb threshold associated with the second word line, wherein the remedial action includes scheduling the data stored in the second word line for a data move operation.

20. The method of claim 19, wherein the read disturb threshold is based on a count of write/erase cycles.

21. The method of claim 20, wherein the read disturb threshold is inversely proportional to the count of write/erase cycles.

22. A method comprising:

in a data storage device that includes a memory and a controller, wherein the memory is configured to store data within a first word line of the memory, performing;

accessing the data from the first word line;

determining, based on a probability threshold, if a remedial action is to be performed with respect to a second word line of the memory; and

if the remedial action is determined to be performed, initiating the remedial action with respect to;

data stored in the second word line, and a different word line of the memory.

23. The method of claim 22, wherein the remedial action includes scheduling the data stored in the second word line for a data move operation.

24. The method of claim 22, wherein the second word line is a neighbor of the first word line, and wherein a third word line is an edge word line of a memory block that includes the first word line and the second word line.

25. The method of claim 22, further comprising determining a number of errors in the data stored in the second word line, wherein determining if the remedial action is to be performed is based on the number of errors in the data stored in the second word line.

26. The method of claim 22, further comprising:

determining a count of write/erase cycles associated with the second word line; and

generating the probability threshold based on the count of write/erase cycles, wherein the second word line is a neighbor of the first word line.

27. The method of claim 22, further comprising:

in response to a determination to perform the remedial action, adding an entry corresponding to the second word line into a reassignment queue;

after the entry is added to the reassignment queue, performing a background operation, wherein the remedial action is performed during the background operation; and

removing the entry from the reassignment queue after the remedial action is performed.