METHOD FOR ADAPTIVE SETTING OF STATE VOLTAGE LEVELS IN NON-VOLATILE MEMORY

• US 20090268516A1
• Filed: 04/29/2008
• Published: 10/29/2009
• Est. Priority Date: 04/29/2008
• Status: Active Grant

• Current Assignee: Western Digital Israel Limited (Western Digital Corporation)
• Original Assignee: SanDisk IL Ltd. (Western Digital Corporation)
• Inventors: Lasser, Menahem, Murin, Mark
• Granted Patent: US 7,808,819 B2
• Time in Patent Office: Days
• US Class Current: 365/185.30
• 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 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/3418 Disturbance prevention or evaluation; Refreshing of disturbed memory data
• CPC Class Codes: G11C 2211/5621 Multilevel programming verification

Abstract

A method in which non-volatile memory device is accessed using voltages which are customized to the device, and/or to portions of the device, such as blocks or word lines of non-volatile storage elements. The accessing can include programming, verifying or reading. By customizing the voltages, performance can be optimized, including addressing changes in threshold voltage which are caused by program disturb. In one approach, different sets of storage elements in a memory device are programmed with random test data. A threshold voltage distribution is determined for the different sets of storage elements. A set of voltages is determined based on the threshold voltage distribution, and stored in a non-volatile storage location for subsequent use in accessing the different sets of storage elements. The set of voltages may be determined at the time of manufacture for subsequent use in accessing data by the end user.

Claims

1. A method for configuring a memory device, comprising:

measuring respective threshold voltage distributions for respective sets of non-volatile storage elements in the memory device, the non-volatile storage elements being multi-level storage elements;

determining a respective set of voltages for each respective set of non-volatile storage elements based on the respective threshold voltage distribution, the respective set of voltages is customized for the respective set of non-volatile storage elements;

storing, in a non-volatile storage location, each set of voltages; and

after the storing, obtaining at least one of the respective sets of voltages from the non-volatile storage location, and performing a write operation involving at least one of the respective sets of non-volatile storage elements using the at least one of the respective sets of voltages.

2. The method of claim 1, wherein:

the voltages comprise verify reference voltages.

3. The method of claim 1, wherein:

the voltages comprise write voltages.

4. The method of claim 1, wherein:

the measuring, determining and storing occur at a manufacturing site, before the memory device is shipped to an end user, and the obtaining and the performing the write operation occur after the device is shipped to the end user.

5. The method of claim 1, wherein:

the measuring, determining, storing, obtaining and the performing the write operation occur after the memory device is shipped to an end user from a manufacturing site.

6. The method of claim 1, wherein:

different sets of voltages are determined for different blocks of non-volatile storage elements in the memory device, each block of non-volatile storage elements is erasable independently of other blocks of non-volatile storage elements.

7. The method of claim 1, wherein:

different sets of voltages are determined for different groups of blocks of non-volatile storage elements in the memory device, each block of non-volatile storage elements is erasable independently of other blocks of non-volatile storage elements, each group comprises one or more blocks, and each block in a group uses the same set of voltages.

8. The method of claim 1, wherein:

different sets of voltages are determined for different groups of word lines of non-volatile storage elements in a block in the memory device, each group comprising one or more word lines.

9. The method of claim 1, wherein:

a plurality of write operations involving the respective sets of non-volatile storage elements are performed using the respective sets of voltages.

10. The method of claim 1, wherein:

the non-volatile storage elements store test data at a time of the measuring; and

the non-volatile storage elements store user data after the write operation.

11. The method of claim 1, wherein:

the non-volatile storage location is in the memory device.

12. A method for configuring a memory device, comprising:

measuring respective threshold voltage distributions for respective sets of non-volatile storage elements in the memory device, the non-volatile storage elements being multi-level storage elements, the measuring includes writing data to the respective sets of non-volatile storage elements;

determining a respective set of voltages for each respective set of non-volatile storage elements based on the respective threshold voltage distribution, the respective set of voltages is customized for the respective set of non-volatile storage elements;

storing, in a non-volatile storage location, each set of voltages; and

after the storing, obtaining at least one of the respective sets of voltages from the non-volatile storage location, and accessing at least one of the respective sets of non-volatile storage elements using the at least one of the respective sets of voltages.

13. The method of claim 12, wherein:

the voltages comprise verify reference voltages.

14. The method of claim 12, wherein:

the voltages comprise write voltages.

15. The method of claim 12, wherein:

the voltages comprise read voltages.

16. The method of claim 12, wherein:

the measuring, determining and storing occur at a manufacturing site, before the memory device is shipped to an end user, and the obtaining and the accessing after the device is shipped to the end user.

17. The method of claim 12, wherein:

the measuring, determining, storing, obtaining and accessing occur after the memory device is shipped to an end user from a manufacturing site.

18. The method of claim 12, wherein:

different sets of voltages are determined for different blocks of non-volatile storage elements in the memory device, each block of non-volatile storage elements is erasable independently of other blocks of non-volatile storage elements.

19. The method of claim 12, wherein:

different sets of voltages are determined for different groups of blocks of non-volatile storage elements in the memory device, each block of non-volatile storage elements is erasable independently of other blocks of non-volatile storage elements, each group comprises one or more blocks, and each block in a group uses the same set of voltages.

20. The method of claim 12, wherein:

different sets of voltages are determined for different groups of word lines of non-volatile storage elements in the memory device, each group comprising one or more word lines.

21. The method of claim 12, wherein:

the data which is written during the measuring comprises test data; and

the at least one of the respective sets of non-volatile storage elements which is accessed during the accessing stores user data.

22. A method for configuring a plurality of separate memory devices, comprising:

for each respective memory device;

(a) measuring one or more respective threshold voltage distributions for one or more respective sets of non-volatile storage elements in the memory device, the non-volatile storage elements being multi-level storage elements;

(b) determining a respective set of voltages for each respective set of non-volatile storage elements based on the respective threshold voltage distribution;

(c) storing the respective set of voltages for each respective set of non-volatile storage elements in a corresponding respective non-volatile storage location, and (d) after the storing, obtaining at least one of the respective sets of voltages from the respective non-volatile storage location, and performing a write operation involving the one or more respective sets of non-volatile storage elements using the at least one of the respective sets of voltages;

the respective sets of voltages are customized to each respective set of non-volatile storage elements, and vary among the plurality of separate memory devices.

23. The method of claim 22, wherein:

a plurality of different sets of voltages are determined for a corresponding plurality of different sets of non-volatile storage elements of one of the memory devices.

24. A method for configuring a plurality of separate memory devices, comprising:

for each respective memory device;

(a) measuring one or more respective threshold voltage distributions for one or more respective sets of non-volatile storage elements in the memory device, the non-volatile storage elements being multi-level storage elements, the measuring includes writing data to the one or more respective sets of non-volatile storage elements;

(b) determining a respective set of voltages for each respective set of non-volatile storage elements based on the respective threshold voltage distribution;

(c) storing the respective set of voltages for each respective set of non-volatile storage elements in a respective non-volatile storage location, and (d) after the storing, obtaining at least one of the respective sets of voltages from the respective non-volatile storage location, and accessing the one or more respective sets of non-volatile storage elements using the at least one of the respective sets of voltages;

the respective sets of voltages are customized to each respective set of non-volatile storage elements, and vary among the plurality of separate memory devices.

25. The method of claim 24, wherein:

a plurality of different sets of voltages are determined for a corresponding plurality of different sets of non-volatile storage elements of one of the memory devices.