BIT LINE CURRENT TRIP POINT MODULATION FOR READING NONVOLATILE STORAGE ELEMENTS

• US 20140211568A1
• Filed: 01/30/2013
• Published: 07/31/2014
• Est. Priority Date: 01/30/2013
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Mui, Man L., Kamei, Teruhiko, Dong, Yingda, Oowada, Ken, Ito, Fumitoshi, Lee, Seungpil, Kato, Yosuke
• Granted Patent: US 8,885,416 B2
• Time in Patent Office: Days
• US Class Current: 365/185.21
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/26 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/28 using differential sensing or reference cells, e.g. dummy cells
• CPC Class Codes: G11C 2211/5621 Multilevel programming verification

Abstract

Upon selecting non-volatile storage elements to be sensed, the system obtains information about the position of these non-volatile storage elements, determines sensing parameters based at least in part on this information, pre-charges a charge storage device and, while maintaining the voltage level of the bit lines of these memory cells at a constant value, applies a reference signal to these non-volatile storage elements for a certain duration of time, afterwards determining whether, for the certain duration of time, the current conducted by these non-volatile storage elements exceeds a predetermined value.

Claims

1. A method for sensing a non-volatile storage element comprising:

obtaining information about the position of the non-volatile storage element;

determining a sensing parameter, at least in part based on the information obtained about the position of the non-volatile storage element;

pre-charging a charge storage device in a sensing circuit, the charge storage device is in communication with a bit line, the non-volatile storage element is in communication with the bit line;

applying a reference signal to the non-volatile storage element while maintaining a constant voltage level on the bit line; and

based on the determined sensing parameter, sensing whether current conducted by the non-volatile element exceeds a pre-determined value in response to the reference signal while maintaining a constant voltage level on the bit line.

2. The method of claim 1, wherein:

the sensing comprises verifying programming of the non-volatile storage element.

3. The method of claim 1, wherein:

the sensing comprises performing a read operation for the non-volatile storage element.

4. The method of claim 1, wherein:

the obtaining information about the position of the non-volatile storage element comprises determining information about the position of the non-volatile storage element with respect to the sensing circuit.

5. The method of claim 1, wherein:

the obtaining information about the position of the non-volatile storage element comprises obtaining the block address of the non-volatile storage element.

6. The method of claim 1, wherein:

the obtaining information about the position of the non-volatile storage element comprises obtaining the word line address of the non-volatile storage element.

7. The method of claim 1, wherein:

the sensing parameter comprises a duration of time for which the non-volatile storage element may be sensed.

8. The method of claim 1, wherein:

the sensing parameter comprises a pre-charge voltage to which the charge storage device is charged.

9. The method of claim 1, wherein:

the applying a reference signal to the non-volatile storage element comprises applying a voltage to the control gate of the non-volatile storage element.

10. A non-volatile storage system, comprising:

a plurality of non-volatile storage elements;

a plurality of bit lines connected to the non-volatile storage elements;

one or more managing circuits in communication with the non-volatile storage elements, the one or more managing circuits obtain information about the position of a non-volatile storage element, determine a sensing parameter at least in part based on the information obtained about the position of the non-volatile storage element, pre-charge a charge storage device in a sensing circuit such that the charge storage device is in communication with a bit line and the non-volatile storage element is in communication with the bit line, apply a reference signal to the non-volatile storage element, and based on the determined sensing parameter sense whether current conducted by the non-volatile element exceeds a pre-determined value while maintaining a constant voltage level on the bit line.

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

the non-volatile storage elements comprise NAND flash memory cells.

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

the one or more managing circuits obtain information about the position of the non-volatile storage element by determining the position of the non-volatile storage element with respect to the sensing circuit.

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

the one or more managing circuits obtain information about the position of the non-volatile storage element by obtaining the block address of the non-volatile storage element.

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

the sensing parameter comprises a duration of time for which the non-volatile storage element may be sensed.

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

the sensing parameter comprises a pre-charge voltage to which the charge storage device is charged.

16. A method for sensing a non-volatile storage element comprising:

obtaining information about the position of the non-volatile storage element;

determining a duration of time for which the non-volatile storage element may be sensed based on the information obtained about the position of the non-volatile storage element;

pre-charging a charge storage device in a sensing circuit, the charge storage device is in communication with a bit line, the non-volatile storage element is in communication with the bit line;

applying a reference signal to the non-volatile storage element while maintaining a constant the voltage level on the bit line; and

after commencing the applying of the reference signal, waiting the determined duration of time and then sensing whether current conducted by the non-volatile element during the determined duration exceeds a pre-determined value in response to the reference signal while maintaining a constant voltage level on the bit line.

17. The method of claim 16, wherein:

the obtaining information about the position of the non-volatile storage element comprises determining information about the position of the non-volatile storage element with respect to the sensing circuit.

18. A method for sensing a non-volatile storage element comprising:

obtaining information about the position of the non-volatile storage element;

determining a pre-charge voltage for a charge storage device in the sensing circuit based on the information obtained about the position of the non-volatile storage element, the charge storage device is in communication with a bit line, the non-volatile storage element is in communication with the sensing circuit;

pre-charging the charge storage device to the determined pre-charge voltage;

applying a reference signal to the non-volatile storage element while maintaining a constant voltage level on the bit line; and

after commencing the applying of the reference signal, waiting a predetermined duration of time and then sensing whether current conducted by the non-volatile element exceeds a pre-determined value in response to the reference signal while maintaining a constant voltage level on the bit line.

19. The method of claim 18, wherein:

the obtaining information about the position of the non-volatile storage element comprises determining information about the position of the non-volatile storage element with respect to the sensing circuit.

20. A non-volatile storage system, comprising:

a plurality of non-volatile storage elements;

a plurality of bit lines connected to the non-volatile storage elements;

one or more managing circuits in communication with the non-volatile storage elements to program the non-volatile storage elements, the one or more managing circuits include one or more sensing circuits to verify and read one or more non-volatile storage elements while maintaining constant the voltage levels on the bit lines connected to the non-volatile storage elements, the one or more sensing circuits each comprise;

a charge storage device,

a pre-charging circuit in communication with the charge storage device in order to pre-charge the charge storage device,

a bit line connection circuit that includes a communication switch that cuts off and connects the bit line to the charge storage device so that the charge storage device is capable of discharging the pre-charge through the bit line and the non-volatile storage element being sensed,

a result detection circuit that determines a state of the charge storage device,

a strobe timer circuit in communication with the result detection circuit, after a duration of time during a sensing operation the strobe timer circuit instructs the result detection circuit to respond to the state of the charge storage device, and

a strobe time determination circuit in communication with the strobe timer circuit that, based on information about the position of the non-volatile element being sensed, determines the duration of time after which the strobe timer circuit will instruct the result detection circuit to respond to the state of the charge storage device.

21. The non-volatile storage system of claim 20 wherein:

the charge storage device comprises one or more capacitors.

22. The non-volatile storage system of claim 20 wherein:

the position of the non-volatile storage element is with respect to a respective sensing circuit.

23. A non-volatile storage system, comprising:

a plurality of non-volatile storage elements;

a plurality of bit lines connected to the non-volatile storage elements;

one or more managing circuits in communication with the non-volatile storage elements to program the non-volatile storage elements, the one or more managing circuits include one or more sensing circuits to verify and read the non-volatile storage elements while maintaining constant voltage levels on the bit lines connected to the non-volatile storage elements, the one or more sensing circuits each comprise;

a charge storage device,

a pre-charging circuit in communication with the charge storage device in order to pre-charge the charge storage device,

a bit line connection circuit that includes a communication switch that cuts off and connects the bit line to the charge storage device so that the charge storage device is capable of discharging the pre-charge through the bit line and the non-volatile storage element,

a result detection circuit that determines a state of the charge storage device;

an adjustable voltage circuit in communication with the pre-charging circuit, the adjustable voltage circuit, based on information about the position of the non-volatile element being sensed, determines the pre-charge voltage to which the pre-charge circuit pre-charges the charge storage device, and

a strobe timer circuit in communication with the result detection circuit, after a duration of time during a sensing operation the strobe timer circuit instructs the result detection circuit to respond to the state of the charge storage device.

24. The non-volatile storage system of claim 23 wherein:

the charge storage device comprises one or more capacitors.

25. The non-volatile storage system of claim 23 wherein:

the position of the non-volatile storage element is with respect to a respective sensing circuit.