PROBABILITY-BASED REMEDIAL ACTION FOR READ DISTURB EFFECTS

• US 20140281766A1
• Filed: 03/13/2013
• Published: 09/18/2014
• Est. Priority Date: 03/13/2013
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: YANG, NIAN NILES, AVILA, CHRIS, SPROUSE, STEVEN, MANOHAR, ABHIJEET, HUANG, YICHAO
• Granted Patent: US 9,575,829 B2
• Time in Patent Office: Days
• US Class Current: 714/721
• 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 method comprising:

in a data storage device that includes a memory and a controller, performing, in response to a request to read data from the memory, wherein the data is located within a first word line of the memory;

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.

2. The method of claim 1, wherein determining, based on the probability threshold, whether to perform the remedial action comprises performing a probability-based test by generating a value and comparing the value to the probability threshold.

3. The method of claim 2, wherein the value is generated randomly, semi-randomly, or pseudo-randomly.

4. The method of claim 2, wherein the remedial action is performed if the value satisfies the probability threshold.

5. The method of claim 1, further comprising selecting the probability threshold based on a read disturb threshold associated with the second word line.

6. The method of claim 5, wherein the read disturb threshold is based on a count of write/erase cycles.

7. The method of claim 6, wherein the read disturb threshold is inversely proportional to the count of write/erase cycles.

8. The method of claim 1, wherein performing the remedial action includes reassigning second data stored in the second word line to a different word line of the memory.

9. The method of claim 8, wherein performing the remedial action further includes reassigning third data stored in a third word line to a second different word line of the memory.

10. The method of claim 9, 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.

11. The method of claim 1, further comprising determining a number of errors in second data in at least a portion of the second word line, wherein determining whether to perform the remedial action is further based on the number of errors in the second data.

12. The method of claim 1, wherein the second word line is a neighbor of the first word line.

13. The method of claim 1, wherein the request is received from a host device while the data storage device is operatively coupled to the host device, and further comprising retrieving the data from the first word line, decoding the data to generate decoded data, and providing the decoded data to the host device in response to the request to read the data.

14. The method of claim 1, wherein performing the remedial action includes adding an entry corresponding to the second word line into a reassignment queue.

15. A data storage device comprising:

a memory; and

a controller, wherein the controller is configured, in response to a request to read data from the memory, wherein the data is located within a first word line of the memory, to access the data from the first word line and to determine, based on a probability threshold, whether to perform a remedial action with respect to a second word line.

16. The data storage device of claim 15, wherein the controller is configured to perform a probability-based test by generating a value and comparing the value to the probability threshold to determine, based on the probability threshold, whether to perform the remedial action.

17. The data storage device of claim 16, wherein the controller is configured to generate the value randomly, semi-randomly, or pseudo-randomly.

18. The data storage device of claim 16, wherein the controller is configured to perform the remedial action if the value satisfies the probability threshold.

19. The data storage device of claim 15, wherein the controller is configured to select the probability threshold based on a read disturb threshold associated with the second word line.

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

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

22. The data storage device of claim 15, wherein the remedial action includes reassigning second data stored in the second word line to a different word line of the memory.

23. The data storage device of claim 22, wherein the remedial action further includes reassigning third data stored in a third word line to a second different word line of the memory.

24. The data storage device of claim 23, 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.

25. The data storage device of claim 15, wherein the controller is configured to determine a number of errors in second data in at least a portion of the second word line, wherein determining whether to perform the remedial action is further based on the number of errors in the second data.

26. The data storage device of claim 15, wherein the second word line is a neighbor of the first word line.

27. The data storage device of claim 15, wherein the controller is configured to retrieve the data from the first word line, to decode the data to generate decoded data, and to provide the decoded data to a host device in response to the request to read the data.

28. The data storage device of claim 15, wherein the controller is configured to perform the remedial action by adding an entry corresponding to the second word line into a reassignment queue.