Adaptive data re-compaction after post-write read verification operations

• US 9,213,601 B2
• Filed: 12/03/2013
• Issued: 12/15/2015
• Est. Priority Date: 12/03/2013
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Tuers, Daniel, Ta, Thomas, Manohar, Abhijeet
• Primary Examiner(s): LAMARRE, GUY J
• Application Number:
  US14/095,881
• Publication Number:
  US 20150154069A1
• Time in Patent Office: 742 Days
• Field of Search: 714/773, 714/758
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• CPC Class Codes: G06F 11/1072 in multilevel memories

Abstract

Approaches are presented for adaptively re-compacting data when errors are found during a post-write verify in a non-volatile memory system, such as flash NAND memory. In one example, user data along with corresponding parity data is written into a block of non-volatile memory. After writing in the user data, but prior to writing the corresponding parity data, the user data is checked. For any word lines that fail this post-write verify, the parity data for the block is adjusted to remove the contribution of any failed word lines before this modified parity data is written into the block. The data corresponding to the failed word lines can then be written elsewhere in the memory system.

Claims

1. A method of operating a non-volatile memory system including one or more non-volatile memory circuits each having one or more arrays of non-volatile memory cells formed along word lines as a plurality of erase blocks, each erase block corresponding to a plurality of word lines, the method comprising:

storing a first plurality of pages of data in a first section of the non-volatile memory system;

subsequently programing the first plurality of pages from the first section into a first plurality of word lines of a first block of the memory system, wherein the first plurality of word lines is less than all of the word lines of the first block;

determining whether the first plurality of data pages were programmed correctly into the first plurality of word lines;

generating one or more pages of parity data from the first plurality of data pages, where the parity data is generated only from those of the first plurality of data pages that were determined to be programmed correctly into the first plurality of word lines; and

writing the generated pages of parity data into one or more second word lines of the first block other than those of the first plurality of word lines.

2. The method of claim 1, further comprising:

in response to determining that one or more of the first plurality of data pages were not programmed correctly, re-programming the pages of data corresponding to those of the first plurality of word lines on which data pages were not programmed correctly from the first section into non-volatile memory on the memory system other than the first block.

3. The method of claim 2, where the non-volatile memory on the memory system other than the first block is a block of non-volatile memory in which data is stored in binary format other than the first section.

4. The method of claim 2, where the non-volatile memory on the memory system other than the first block is a block of non-volatile memory in which data is stored in multi-state format other than the first section.

5. The method of claim 2, wherein the memory system updates a logical to physical mapping between logical pages of data and the location in which the logical pages are written to reflect the re-programming the pages of data corresponding to those of the first plurality of word lines on which data pages were not programmed correctly.

6. The method of claim 1, wherein the memory system further includes a controller circuit and the first section is RAM memory on the controller circuit.

7. The method of claim 1, wherein the first section is one or more blocks of non-volatile memory in which the first plurality of pages of data are stored in binary format.

8. The method of claim 7, further comprising receiving the first plurality of pages from a host to which the memory system is connected and writing the first plurality of pages into the first section.

9. The method of claim 7, wherein the first plurality of pages are programmed into the first plurality of word lines in a multi-state format in which data from N word lines in the first section are programmed into each of the word lines of the first plurality, where N is two or larger.

10. The method of claim 9, wherein the programming of the first plurality of pages is performed as an on-chip operation.

11. The method of claim 1, wherein the first plurality of word lines and the second word lines correspond to all of the word lines of the first block.

12. The method of claim 1, wherein the determining of whether the first plurality of data pages were programmed correctly is performed subsequent to programming all of the first plurality of data pages into the first plurality of word lines.

13. The method of claim 1, wherein the determining of whether the first plurality of data pages were programmed correctly is performed for one or more of first plurality of data pages prior to programming all of the first plurality of data pages.

14. The method of claim 1, wherein the determining of whether a data page was programmed correctly comprises determining whether the amount of error of the data page exceeds limit.

15. The method of claim 1, further comprising:

prior to programing the first plurality of pages from the first section into a first plurality of word lines of a first block of the memory system, determining whether the first plurality of pages of data as stored in the first section have an amount of error exceeding a limit.

17. The method of claims 1, wherein the one or more second word lines is a plurality of word lines.

18. The method of claim 1, further comprising:

maintaining a record of the first word lines in which data pages where determined to not be programmed correctly.

19. The method of claim 18, wherein the first word lines in which data pages where determined to not be programmed correctly are marked as defective in the record.

16. The method of clam 1, wherein generating the pages of parity data includes modifying previously generated pages of parity data to exclude the contribution thereto of data pages that were determined to not be programmed correctly.