METHOD FOR CONTROLLED PROGRAMMING OF NON-VOLATILE MEMORY EXHIBITING BIT LINE COUPLING

• US 20070086247A1
• Filed: 10/14/2005
• Published: 04/19/2007
• Est. Priority Date: 10/14/2005
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Li, Yan, Lutze, Jeffrey, Chan, Siu
• Granted Patent: US 7,286,406 B2
• Time in Patent Office: Days
• US Class Current: 365/185.180
• CPC Class Codes: G11C 16/3418 Disturbance prevention or evaluation; Refreshing of disturbed memory data
• CPC Class Codes: G11C 16/3427 Circuits or methods to prevent or reduce disturbance of the state of a memory cell when neighbouring cells are read or written

Abstract

The effects of bit line-to-bit line coupling in a non-volatile memory are addressed. An inhibit voltage is applied on a bit line of a storage element to be programmed to inhibit programming during a portion of a program voltage. The inhibit voltage is subsequently removed during the program voltage to allow programming to occur. Due to the proximity of bit lines, the change in the bit line voltage is coupled to a neighboring unselected bit line, reducing the neighboring bit line voltage to a level which might be sufficient to open a select gate and discharge a boost voltage. To prevent this, the select gate voltage is temporarily adjusted during the change in the bit line voltage to ensure that the biasing of the select gate on the unselected bit line is not sufficient to open the select gate.

Claims

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

applying a program voltage to at least first and second non-volatile storage elements in a set of non-volatile storage elements, the first and second non-volatile storage elements being coupled to respective first and second bit lines via respective first and second select gates;

partially inhibiting programming of the first non-volatile storage element during the program voltage by controlling a voltage applied to the first bit line;

inhibiting programming of the second non-volatile storage element during the program voltage by providing an inhibit voltage on the second bit line; and

adjusting a select gate voltage which is applied to the second select gate during a transition in the voltage applied to the first bit line during the program voltage.

2. The method of claim 1, wherein the transition comprises a voltage drop which causes a drop in the inhibit voltage provided on the second bit line due to coupling between the first and second bit lines.

3. The method of claim 2, wherein the voltage drop would be sufficient to cause the second select gate to turn on if the select gate voltage were not adjusted in the adjusting step.

4. The method of claim 1, wherein the transition comprises a reduction from a first voltage level which inhibits programming of the first non-volatile storage element, to a second voltage level which allows programming of the first non-volatile storage element.

5. The method of claim 1, wherein the adjusting comprises temporarily reducing the select gate voltage.

6. The method of claim 1, wherein the select gate voltage is also applied to the first select gate.

7. The method of claim 6, wherein the adjusting comprises temporarily reducing the select gate voltage from a steady state level which is sufficiently low relative to the inhibit voltage provided on the second bit line to maintain the second select gate closed, and sufficiently high relative to the voltage applied to the first bit line, during at least a portion of the program voltage, to maintain the first select gate open.

8. The method of claim 1, wherein the program voltage comprises a voltage pulse in a series of voltage pulses.

9. The method of claim 1, wherein the transition comprises a reduction from a first voltage level which inhibits programming of the first non-volatile storage element, during a first portion of the program voltage, to a second level which allows programming of the first non-volatile storage element, during a second portion of the program voltage.

10. The method of claim 1, wherein the first and second non-volatile storage elements are arranged in respective NAND strings.

11. The method of claim 1, wherein the program voltage is applied to the first and second non-volatile storage elements via a common word line.

12. A method for programming non-volatile storage, comprising:

controlling a rate of programming of a first non-volatile storage element, in a set of non-volatile storage elements, by controlling a voltage applied to a first bit line to which the first non-volatile storage element is coupled via a first select gate;

inhibiting programming of a second non-volatile storage element, in the set of non-volatile storage elements, by providing an inhibit voltage on a second bit line to which the second non-volatile storage element is coupled via a second select gate; and

adjusting a select gate voltage applied to the second select gate in accordance with a change in the voltage applied to the first bit line.

13. The method of claim 12, wherein the change comprises a change from a first voltage level which inhibits programming of the first non-volatile storage element, to a second voltage level which allows programming of the first non-volatile storage element.

14. The method of claim 12, wherein the adjusting comprising temporarily changing the select gate voltage from a steady state level.

15. The method of claim 12, wherein the first and second non-volatile storage elements are arranged in respective NAND strings.

16. The method of claim 12, wherein the adjusting of the select gate voltage compensates for a change in the inhibit voltage on the second bit line which is caused, through coupling, by the change in the voltage applied to the first bit line, thereby maintaining the second select gate closed during the coupling.

17. The method of claim 12, wherein the change comprises a change from a first voltage level which inhibits programming of the first non-volatile storage element, during a first portion of a program voltage applied thereto, to a second voltage level which allows programming of the first non-volatile storage element, during a second portion of the program voltage.

18. The method of claim 17, wherein the program voltage is applied to the first and second non-volatile storage elements via a common word line.

19. The method of claim 17, wherein the program voltage comprises a voltage pulse in a series of voltage pulses.

20. The method of claim 12, wherein the select gate voltage is also applied to the first select gate.

21. A method for programming non-volatile storage, comprising:

applying a program voltage to at least first and second non-volatile storage elements in a set of non-volatile storage elements, the first and second non-volatile storage elements being coupled to respective first and second bit lines via respective first and second select gates;

applying a voltage to the first bit line;

applying a select gate voltage to the second select gate; and

adjusting the select gate voltage in accordance with a change in the voltage applied to the first bit line to maintain the second select gate closed.

22. The method of claim 21, wherein the change comprises a change from a first voltage level which inhibits programming of the first non-volatile storage element, to a second voltage level which allows programming of the first non-volatile storage element.

23. The method of claim 21, wherein the adjusting comprises temporarily changing the select gate voltage from a steady state level.

24. The method of claim 21, wherein the change comprises a change from a first voltage level which inhibits programming of the first non-volatile storage element, during a first portion of the program voltage, to a second voltage level which allows programming of the first non-volatile storage element, during a second portion of the program voltage.

25. The method of claim 21, wherein the program voltage is applied to the first and second non-volatile storage elements via a common word line.

26. The method of claim 21, wherein the first and second non-volatile storage elements are arranged in respective NAND strings.

27. The method of claim 21, wherein the program voltage comprises a voltage pulse in a series of voltage pulses.

28. The method of claim 21, wherein the adjusting of the select gate voltage compensates for a change in a voltage on the second bit line which is caused, through coupling, by the change in the voltage applied to the first bit line.