NONVOLATILE MEMORY SYSTEM STORING SYSTEM DATA IN MARGINAL WORD LINES

• US 20160180926A1
• Filed: 12/19/2014
• Published: 06/23/2016
• Est. Priority Date: 12/19/2014
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Darragh, Neil, Young, Robert George
• Granted Patent: US 10,141,049 B2
• Time in Patent Office: Days
• 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
• CPC Class Codes: G06F 3/0604 Improving or facilitating administration, e.g. storage management
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/10 Programming or data input circuits
• CPC Class Codes: G11C 16/26 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 2029/0411 Online error correction
• CPC Class Codes: G11C 29/52 Protection of memory contents; Detection of errors in memory contents
• CPC Class Codes: G11C 8/08 Word line control circuits, e.g. drivers, boosters, pull-up circuits, pull-down circuits, precharging circuits, for word lines
• CPC Class Codes: G11C 8/14 Word line organisation; Word line lay-out

Abstract

To make more efficient use of storage capacity, a non-volatile storage system will store system data on marginal word lines. In one embodiment, a marginal word line is a word line that is not suitable to store host data because it is not sufficiently reliable for properly programming and reading the host data.

Claims

1. A non-volatile storage system, comprising:

a first non-volatile memory structure that includes a plurality of word line units that each include one word line and a plurality of non-volatile storage elements, the word line units are arranged in blocks, the plurality of word line units include a first word line unit in a first block and a second word line unit in the first block; and

one or more control circuits in communication with the first non-volatile memory structure, the one or more control circuits are configured to write host data to the first word line unit, the one or more control circuits are configured to not write host data to the second word line unit, the one or more control circuits are configured to write system data associated with host data to the second word line unit.

2. The non-volatile storage system of claim 1, wherein:

the second word line unit is not suitable to store host data because of poor reliability of the second word line unit based on one or more physical characteristics of the second word line unit.

3. The non-volatile storage system of claim 1, wherein:

the second word line unit is not a valid address to store host data.

4. The non-volatile storage system of claim 1, wherein:

the one or more control circuits are configured to recover the system data from one or more locations other than the second word lint unit if the one or more control circuits cannot successfully read the system data from the second word line unit.

5. The non-volatile storage system of claim 1, wherein:

the one or more control circuits are configured to write the host data to the first word line unit as multi-level data with multiple bits being stored per non-volatile storage element; and

the one or more control circuits are configured to write the system data to the second word line unit as binary data with one bit being stored per non-volatile storage element.

6. The non-volatile storage system of claim 1, wherein:

the one or more control circuits are configured to write the host data to the first word line unit using a first error correction coding; and

the one or more control circuits are configured to write the system data to the second word line unit using a second error correction coding that has lower code rate than the first error correction coding.

7. The non-volatile storage system of claim 1, wherein:

the one or more control circuits are configured to write multiple redundant copies of the system data to the second word line unit.

8. The non-volatile storage system of claim 7, wherein:

the one or more control circuits are configured to read the system data by accessing sensed information for the second word line unit, assessing a first page of the sensed information, and attempting to recover a first copy of the multiple redundant copies of the system data using error correction; and

the one or more control circuits are configured to assess a second page of the sensed information and attempt to recover a second copy of the multiple redundant copies of the system data using error correction if the first copy cannot be recovered.

9. The non-volatile storage system of claim 8, wherein:

the one or more control circuits are configured recover the system data from one or more locations other than the second word lint unit if the first copy cannot be recovered and the second copy cannot be recovered.

10. The non-volatile storage system of claim 1, wherein:

the one or more control circuits are configured to write the system data to the second word line unit by programming the system data to non-volatile storage elements connected to a dummy word line.

11. The non-volatile storage system of claim 1, wherein:

the one or more control circuits are configured to write the system data to the second word line unit by programming the system data to non-volatile storage elements connected to a word line determined to have failed.

12. A method of operating non-volatile storage system, the non-volatile storage system includes word line units that each include a word line and a plurality of non-volatile storage elements, the method comprising:

storing host data in a first word line unit of a first block; and

storing system data associated with the host data in a second word line unit of the first block, the second word line unit does not store host data, the second word line unit is not a valid address to store host data.

13. The method of claim 12, wherein:

the non-volatile storage system is configured not to write host data to the second word line unit.

14. The method of claim 12, wherein:

the second word line unit is not suitable to store host data because of poor reliability of the second word line unit based on one or more physical characteristics of the second word line unit.

15. The method of claim 12, further comprising:

attempting to read the system data from the second word line unit; and

recovering the system data from one or more locations other than the second word line unit if the attempting to read the system data from the second word line unit is unsuccessful.

16. The method of claim 12, wherein:

the storing host data comprises programming the host data as multi-level data with multiple bits being stored per non-volatile storage element; and

the storing system data comprises programming the system data as binary data with one bit being stored per non-volatile storage element.

17. The method of claim 12, wherein:

the storing host data comprises programming the host data using a first error correction coding; and

the storing system data comprises programming the system data using a second error correction coding that has a lower code rate than the first error correction coding.

18. The method of claim 12, wherein:

the storing system data comprises programming multiple redundant copies of the system data to the second word line unit.

19. The method of claim 18, further comprising:

reading the system data by accessing sensed information for the second word line unit, assessing a first page of the sensed information, and attempting to recover a first copy of the multiple redundant copies of the system data using error correction; and

assessing a second page of the sensed information and attempting to recover a second copy of the multiple redundant copies of the system data using error correction if the first copy cannot be recovered.

20. The method of claim 12, wherein:

the storing system data comprises programming the system data to non-volatile storage elements connected to a dummy word line.

21. The method of claim 12, wherein:

the storing system data comprises programming the system data to non-volatile storage elements connected to a word line a word line determined to have failed.

22. A method of operating non-volatile storage system, the non-volatile storage system includes word line units that each include a word line and a plurality of non-volatile storage elements, the method comprising:

storing host data in a first word line unit of a first block; and

storing system data associated with the host data in a second word line unit of the first block, the second word line unit does not store host data, the second word line unit is not suitable to store host data because of poor reliability of the second word line unit based on one or more physical characteristics of the second word line unit.

23. The method of claim 22, wherein:

the storing host data comprises programming the host data as multi-level data with multiple bits being stored per non-volatile storage element; and

the storing system data comprises programming the system data as binary data with one bit being stored per non-volatile storage element.

24. The method of claim 23, wherein:

the storing host data comprises programming the host data using a first error correction coding; and

the storing system data comprises programming the system data using a second error correction coding that has a lower code rate than the first error correction coding.

25. The method of claim 24, wherein:

the storing system data comprises programming multiple redundant copies of the system data to the second word line unit.

26. A non-volatile storage system, comprising:

a plurality of memory die, each memory die includes one or more memory structures, each memory structure includes a plurality of word line units that each include a word line and a plurality of non-volatile storage elements; and

one or more control circuits in communication with the plurality of memory die via a plurality of channels, each channel connects a subset of the memory die to the one or more control circuits, the one or more control circuits receive host data and create a unit of data that includes the host data and system data associated with the host data, the one or more control circuits program the unit of data across multiple memory die of the plurality of memory die so that the unit of data is stored in a first set of word line units and a marginal word line unit, the marginal word line unit is not suitable to store host data because of poor reliability of the marginal word line unit based on one or more physical characteristics of the marginal word line unit, no host data is stored in the marginal word line unit.