Charge packet metering for coarse/fine programming of non-volatile memory

• US 7,068,539 B2
• Filed: 01/27/2004
• Issued: 06/27/2006
• Est. Priority Date: 01/27/2004
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Mokhlesi, Nima, Guterman, Daniel C., Fong, Yupin
• Primary Examiner(s): Nguyen, Viet Q.
• Application Number:
  US10/766,116
• Publication Number:
  US 20050162923A1
• Time in Patent Office: 882 Days
• Field of Search: 365/185.18, 365/185.22, 365/185.24, 365/185.25, 365/185.28
• US Class Current: 365/185.18
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 16/10 Programming or data input circuits
• CPC Class Codes: G11C 2211/5621 Multilevel programming verification
• CPC Class Codes: G11C 2211/5624 Concurrent multilevel programming and programming verification

Abstract

A non-volatile memory device is programmed by first performing a coarse programming process and subsequently performing a fine programming process. The coarse/fine programming methodology is enhanced by using an efficient verification scheme that allows some non-volatile memory cells to be verified for the coarse programming process while other non-volatile memory cells are verified for the fine programming process. The fine programming process can be accomplished using current sinking, charge packet metering or other suitable means.

Claims

1. A method for programming, comprising:

performing a coarse programming phase for a non-volatile storage element until said non-volatile storage element reaches a first condition; and

performing a fine programming phase for said non-volatile storage element by metering charge to said non-volatile storage element, said metering charge to said non-volatile storage element comprises charging a charge storage element, applying a program signal to said non-volatile storage element, and discharging said charge storage element through said non-volatile storage element.

2. A method according to claim 1, wherein:

said fine programming phase is commenced for said non-volatile storage element subsequent to said coarse programming phase being completed for said non-volatile storage element.

3. A method according to claim 1, wherein:

said charging a charge storage element includes connecting a capacitor to a power supply and charging said capacitor.

4. A method according to claim 1, wherein said charging said charge storage element, applying said program signal, and discharging said charge storage element comprise:

pre-charging a bit line associated with said non-volatile storage element;

causing said bit line to be in a floating state after said pre-charging;

applying a common program signal to said non-volatile storage element; and

discharging said charge storage element through said non-volatile storage element.

6. A method according to claim 1, wherein said metering charge to said non-volatile storage element comprises:

switching power supplies in a charge metering system.

8. A method according to claim 1, wherein:

said coarse programming mode does not include metering charge to said non-volatile storage element.

9. A method according to claim 1, wherein:

said a non-volatile storage element is a multi-state flash memory device.

10. A method according to claim 1, wherein:

said program signal is applied to multiple non-volatile storage elements along a common word line.

5. A method for programming, comprising:

performing a coarse programming phase for a non-volatile storage element until said non-volatile storage element reaches a first condition; and

performing a fine programming phase for said non-volatile storage element by metering charge to said non-volatile storage element, said metering charge to said non-volatile storage element comprises switching capacitors in a charge metering system.

7. A method for programming, comprising:

performing a coarse programming phase for a non-volatile storage element until said non-volatile storage element reaches a first condition; and

performing a fine programming phase for said non-volatile storage element by metering charge to said non-volatile storage element, said metering charge to said non-volatile storage element comprises switching a variable power supply in a charge metering system.

11. A method for programming, comprising:

performing a coarse programming process on a non-volatile storage element;

determining that said non-volatile storage element should switch to a fine programming process; and

performing said fine programming process in response to determining that said non-volatile storage element should switch to said fine programming process, said fine programming process comprises;

pre-charging a control line for said non-volatile storage element, and

discharging said control line via said non-volatile storage element in order to program said non-volatile storage element.

12. A method according to claim 11, wherein:

said step of pre-charging a control line includes charging a capacitor.

13. A method according to claim 11, wherein:

said step of pre-charging a control line includes connecting a charge storage device to a power supply, said charge storage device is connected to said non-volatile storage element; and

said step of discharging said control line includes disconnecting said power supply from said charge storage device.

14. A method according to claim 11, wherein:

said control line is a bit line for multiple non-volatile storage elements.

15. A method according to claim 11, wherein:

said control line is pre-charged using a variable power supply; and

said fine programming process comprises changing said variable power supply to provide a signal appropriate for said fine programming process.

16. A method according to claim 11, wherein:

said control line is pre-charged during said coarse programming process using a first power supply;

said control line is pre-charged during said fine programming process using a second power supply; and

said fine programming process includes switching from said first power supply to said second power supply.

17. A method according to claim 11, wherein:

said control line is pre-charged during said fine programming process using a first charge storage device;

said control line is pre-charged when not in said fine programming process using a second charge storage device; and

said fine programming process includes switching from said second charge storage device to said first charge storage device.

18. A method according to claim 11, wherein:

said non-volatile storage element is a multi-state flash memory device.

19. A method for programming, comprising:

performing a coarse programming phase for a non-volatile storage element until said non-volatile storage element reaches a first condition; and

performing a fine programming phase for said non-volatile storage element by metering charge to said non-volatile storage element, said metering charge to said non-volatile storage element comprises switching charge storage devices.