Tracking cell erase counts of non-volatile memory

• US 9,153,331 B2
• Filed: 03/13/2013
• Issued: 10/06/2015
• 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: D'Abreu, Manuel Antonio, Pantelakis, Dimitris, Skala, Stephen
• Primary Examiner(s): NGUYEN, HIEN N
• Application Number:
  US13/800,637
• Publication Number:
  US 20140269069A1
• Time in Patent Office: 937 Days
• US Class Current: 1/1
• CPC Class Codes: G11C 16/06 Auxiliary circuits, e.g. for writing into memory
• CPC Class Codes: G11C 16/16 for erasing blocks, e.g. arrays, words, groups
• CPC Class Codes: G11C 16/3495 Circuits or methods to detect or delay wearout of nonvolatile EPROM or EEPROM memory devices, e.g. by counting numbers of erase or reprogram cycles, by using multiple memory areas serially or cyclically

Abstract

A data storage device includes a memory and a controller and may perform a method that includes updating, in a controller of the data storage device, a value of a particular write/erase (W/E) counter of a set of counters in response to an erase operation to a particular region of the non-volatile memory that is tracked by the particular W/E counter and that includes a storage element that is tracked by a particular cell erase counter of the set of counters. The method includes, in response to the value of the particular W/E counter indicating that a count of erase operations to the particular region satisfies a first threshold, initiating a remedial action to the particular region of the non-volatile memory at least partially based on the value of the particular cell erase counter.

Claims

1. A method comprising:

in a data storage device that includes a controller and a non-volatile memory, performing;

in response to an erase operation to a particular region of the non-volatile memory;

updating, in the controller, a value of a particular cell erase counter of a plurality of cell erase counters, wherein each cell erase counter of the plurality of cell erase counters is associated with a storage element in the particular region; and

updating, in the controller, a value of a write/erase (W/E) counter wherein the W/E counter is associated with the particular region; and

in response to the value of the W/E counter satisfying a first threshold, initiating a remedial action to the particular region of the non-volatile memory at least partially based on the value of the particular cell erase counter.

2. The method of claim 1, wherein erase operations to a first region of the non-volatile memory are tracked by a first W/E counter, wherein a first cell erase count of a first storage element in the first region is tracked by a first cell erase counter, and wherein the first region corresponds to a first set of erase blocks of the non-volatile memory, and wherein erase operations to a second region of the non-volatile memory are tracked by a second W/E counter, wherein a second cell erase count of a second storage element in the second region is tracked by a second cell erase counter, and wherein the second region corresponds to a second set of erase blocks of the non-volatile memory.

3. The method of claim 2, wherein the first set of erase blocks comprises a single erase block and wherein the second set of erase blocks comprises another single erase block.

4. The method of claim 1, wherein in response to a write operation, the value of the particular cell erase counter is updated in response to the storage element being set from an erase state to a non-erase state and is not updated in response to the storage element remaining in the erase state.

5. The method of claim 1, wherein the controller maintains a set of cell erase counters to track cell erase counts for multiple storage elements in a word line in the particular region, and wherein the remedial action is selected based at least partially on a number of the cell erase counts that exceed a first cell erase threshold.

6. The method of claim 1, wherein the controller maintains multiple sets of cell erase counters to track cell erase counts for multiple storage elements in multiple word lines in the particular region, and wherein the controller is configured to select the remedial action by determining a number of the word lines having cell erase counts that exceed a first cell erase threshold and comparing the number to a second threshold.

7. The method of claim 1, wherein initiating the remedial action includes scheduling an erase block in the particular region to be unused.

8. The method of claim 1, wherein initiating the remedial action includes setting a flag to indicate data and parity interleaving is to be applied to the particular region.

9. The method of claim 1, wherein initiating the remedial action includes setting a flag to indicate adaptive reading is to be applied to the particular region.

10. The method of claim 1, further comprising:

during a session shut-down operation of the data storage device, storing cell erase values of the plurality of cell erase counters and a W/E value of the W/E counter for the particular region to the non-volatile memory; and

during a session initialization operation of the data storage device, retrieving the stored cell erase values and the W/E value from the non-volatile memory and initializing counters according to the stored values.

11. The method of claim 1, wherein the non-volatile memory includes a flash memory.

12. A data storage device comprising:

a non-volatile memory; and

a controller including a set of write/erase (W/E) counters and a set of cell erase counters, wherein the controller is configured to update a value of a particular write/erase (W/E) counter in response to an erase operation to a particular region of the non-volatile memory that is tracked by the particular W/E counter and update a value of a particular cell erase counter of a plurality of cell erase counters, wherein each cell erase counter of the plurality of cell erase counters is associated with a storage element in the particular region, and

wherein, in response to the value of the particular W/E counter indicating that a count of erase operations to the particular region satisfies a first threshold, the controller is configured to initiate a remedial action to the particular region of the non-volatile memory at least partially based on the value of the particular cell erase counter.

13. The data storage device of claim 12, wherein erase operations to a first region of the non-volatile memory are tracked by a first W/E counter, wherein a first cell erase count of a first storage element in the first region is tracked by a first cell erase counter, and wherein the first region corresponds to a first set of erase blocks of the non-volatile memory, and wherein erase operations to a second region of the non-volatile memory are tracked by a second W/E counter, wherein a second cell erase count of a second storage element in the second region is tracked by a second cell erase counter, and wherein the second region corresponds to a second set of erase blocks of the non-volatile memory.

14. The data storage device of claim 13, wherein the first set of erase blocks comprises a single erase block and wherein the second set of erase blocks comprises another single erase block.

15. The data storage device of claim 12, wherein in response to a write operation, the controller is configured to update the value of the particular cell erase counter in response to the storage element being set from an erase state to a non-erase state and to not update the value in response to the storage element remaining in the erase state.

16. The data storage device of claim 12, wherein the controller is configured to maintain a set of cell erase counters to track cell erase counts for multiple storage elements in a word line in the particular region, and wherein the controller is configured to select the remedial action based at least partially on a number of the cell erase counts that exceed a first cell erase threshold.

17. The data storage device of claim 12, wherein the controller is configured to maintain multiple sets of cell erase counters to track cell erase counts for multiple storage elements in multiple word lines in the particular region, and wherein the controller is configured to select the remedial action by determining a number of the word lines having cell erase counts that exceed a first cell erase threshold and comparing the number to a second threshold.

18. The data storage device of claim 12, wherein the controller is configured to initiate the remedial action by scheduling an erase block in the particular region to be unused.

19. The data storage device of claim 12, wherein the controller is configured to initiate the remedial action by setting a flag to indicate data and parity interleaving is to be applied to the particular region.

20. The data storage device of claim 12, wherein the controller is configured to initiate the remedial action by setting a flag to indicate adaptive reading is to be applied to the particular region.

21. The data storage device of claim 12, wherein the controller is configured to store values of the set of W/E counters and of the set of cell erase counters to the non-volatile memory during a session shut-down operation and to retrieve the stored values from the non-volatile memory and initialize the set of W/E counters of the set of cell erase counters according to the stored values during a session initialization operation.

22. The data storage device of claim 12, wherein the non-volatile memory includes a flash memory.