Compensating for coupling during programming

• US 7,885,119 B2
• Filed: 07/20/2006
• Issued: 02/08/2011
• Est. Priority Date: 07/20/2006
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Li, Yan
• Primary Examiner(s): Elms; Richard
• Assistant Examiner(s): Nguyen; Hien N
• Application Number:
  US11/459,001
• Publication Number:
  US 20080019185A1
• Time in Patent Office: 1,664 Days
• Field of Search: 365/185.11, 365/185.17, 365/185.09, 365/185.18, 365/185.21, 365/185.23
• US Class Current: 365/185.22
• CPC Class Codes: G11C 16/3418 Disturbance prevention or evaluation; Refreshing of disturbed memory data
• CPC Class Codes: G11C 8/10 Decoders

Abstract

Shifts in the apparent charge stored on a floating gate (or other charge storing element) of a non-volatile memory cell can occur because of the coupling of an electric field based on the charge stored in adjacent floating gates (or other adjacent charge storing elements). To compensate for this coupling, the read or programming process for a given memory cell can take into account the programmed state of an adjacent memory cell. To determine whether compensation is needed, a process can be performed that includes sensing information about the programmed state of an adjacent memory cell (e.g., on an adjacent bit line or other location).

Claims

1. A method of programming non-volatile storage, comprising:

programming non-volatile storage elements to a coarse verification level associated with a particular programmed state;

performing additional programming of a first subset of said non-volatile storage elements to a first fine final target level associated with said particular programmed state; and

performing additional programming of a second subset of said non-volatile storage elements to a second fine final target level associated with said particular programmed state.

2. A method according to claim 1, wherein:

said particular programmed state is one of multiple programmed states;

said non-volatile storage elements are part of an array of non-volatile storage elements; and

said non-volatile storage elements are targeted for programming to said particular programmed state.

3. A method according to claim 1, wherein:

said first subset of said non-volatile storage elements are being compensated for floating gate to floating gate coupling; and

said second subset of said non-volatile storage elements are not being compensated for floating gate to floating gate coupling.

4. A method according to claim 1, wherein:

said first subset of said non-volatile storage elements are adjacent to one or more neighboring non-volatile storage elements in a first condition; and

said second subset of said non-volatile storage elements are not adjacent to one or more neighboring non-volatile storage elements in said first condition.

5. A method according to claim 4, wherein:

first fine final target level is lower than said second fine final target level.

6. A method according to claim 1, wherein:

said performing additional programming of said first subset of said non-volatile storage elements and said performing additional programming of said second subset of said non-volatile storage elements include applying a common set of program pulses to control gates for said first subset of said non-volatile storage elements and said second subset of said non-volatile storage elements.

7. A method according to claim 1, wherein:

said programming non-volatile storage elements to said coarse verification level includes applying a first bit line voltage for said non-volatile storage elements; and

said performing additional programming of said first subset of said non-volatile storage elements and said performing additional programming of said second subset of said non-volatile storage elements include applying one or more bit line voltages that are different than said first bit line voltage for said non-volatile storage elements.

8. A method according to claim 1, wherein:

said non-volatile storage elements are NAND flash memory devices.

9. A method according to claim 1, wherein:

said non-volatile storage elements are multi-state flash memory devices.

10. A method of programming a set of non-volatile storage elements, comprising:

programming a first subset of said non-volatile storage elements to a first programmed state using one coarse verification level with a first coarse programming process and two fine verification levels with a fine programming process; and

programming additional subsets of non-volatile storage elements to additional programmed states using one coarse verification level for each additional programmed state with said first coarse programming process and one fine verification level for each additional programmed state with said fine programming process.

11. A method according to claim 10, wherein:

said first subset of said non-volatile storage elements and said additional subsets of non-volatile storage elements are connected to a common word line.

12. A method according to claim 10, wherein:

said programming said first subset and said programming said additional subsets includes applying a common programming signal to said first subset of said non-volatile storage elements and said additional subsets of non-volatile storage elements.

13. A method according to claim 10, wherein:

said first subset of said non-volatile storage elements and said additional subsets of non-volatile storage elements are multi-state flash memory devices.

14. A method according to claim 10, wherein:

some of said first subset of said non-volatile storage elements are being compensated for floating gate to floating gate coupling and other of said first subset of said non-volatile storage elements are not being compensated for floating gate to floating gate coupling; and

said additional subsets of said non-volatile storage elements are not being compensated for floating gate to floating gate coupling.

15. A method according to claim 10, wherein:

said two fine verification levels include a first verification level and a second verification level;

some of said first subset of said non-volatile storage elements that are adjacent to non-volatile storage elements targeted to be in a first condition use said first verification level; and

other of said first subset of said non-volatile storage elements that are not adjacent to non-volatile storage elements targeted to be in said first condition use said second verification level.

16. A method according to claim 15, wherein:

first verification level is lower than said second verification level.

17. A method of programming a set of non-volatile storage elements, comprising:

programming a first set of non-volatile storage elements to a particular programmed state using a particular final target level for said particular programmed state, said first set of non-volatile storage elements are adjacent to non-volatile storage elements that have been identified for programming to a different programmed state; and

programming a second set of non-volatile storage elements to said particular programmed state using another final target level for said particular programmed state, said second set of non-volatile storage elements are not adjacent to non-volatile storage elements that have been identified for programming to said different programmed state.

18. A method according to claim 17, wherein:

said particular final target level is lower than said another final target level.

19. A method according to claim 17, wherein:

said first set of non-volatile storage elements and said second set of non-volatile storage elements are associated with a common control line.

20. A method according to claim 19, wherein:

said common control line is a word line; and

said programming said first set of non-volatile storage elements and said programming said second set of non-volatile storage elements includes applying a common program signal to said word line.

21. A method according to claim 17, wherein:

said first set of non-volatile storage elements and said second set of non-volatile storage elements are multi-state flash memory devices.

22. A method of programming a set of non-volatile storage elements, comprising:

programming a first set of non-volatile storage elements to a particular programmed state using a particular final target level for said particular programmed state, said first set of non-volatile storage elements are adjacent to additional non-volatile storage elements that have been identified for programming to a different programmed state;

programming a second set of non-volatile storage elements to said particular programmed state using another final target level for said particular programmed state; and

programming said additional non-volatile storage elements to said different programmed state using a different final target level.

23. A method according to claim 22, further comprising:

programming a third set of non-volatile storage elements to another programmed state, said another programmed state is between said particular programmed state and said different programmed state.

24. A method according to claim 22, wherein:

said first set of non-volatile storage elements, said second set of non-volatile storage elements and said additional non-volatile storage elements are associated with a common control line; and

said programming said first set of non-volatile storage elements includes applying a program signal on said common control line.

25. A method according to claim 22, wherein:

said first set of non-volatile storage elements, said second set of non-volatile storage elements and said additional non-volatile storage elements are multi-state flash memory devices.