Variable initial program voltage magnitude for non-volatile storage

• US 7,564,715 B2
• Filed: 03/31/2007
• Issued: 07/21/2009
• Est. Priority Date: 02/20/2007
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Mokhlesi, Nima
• Primary Examiner(s): AUDUONG, GENE NGHIA
• Application Number:
  US11/694,990
• Publication Number:
  US 20080198665A1
• Time in Patent Office: 843 Days
• Field of Search: 365/185.03, 365/185.17, 365/185.19, 365/185.22, 365/185.24
• US Class Current: 365/185.19
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input 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 16/3454 Arrangements for verifying correct programming or for detecting overprogrammed cells
• CPC Class Codes: G11C 16/3459 Circuits or methods to verify correct programming of nonvolatile memory cells
• CPC Class Codes: G11C 2211/5621 Multilevel programming verification
• CPC Class Codes: G11C 5/147 Voltage reference generators, voltage or current regulators; Internally lowered supply levels; Compensation for voltage drops G11C5/141 takes precedence
• CPC Class Codes: G11C 8/10 Decoders

Abstract

Multiple programming processes are performed for a plurality of non-volatile storage elements. Each of the programming process operates to program at least a subset of said non-volatile storage elements to a set of target conditions using program pulses. In one embodiment, a first programming pass includes soft programming and additional programming passes include the programming of data. In another embodiment, all of the programming process include programming data. For at least a subset of said programming processes, a program pulse associated with achieving a particular result for a respective programming process is identified. The identified program pulse is used to adjust programming for a subsequent programming process.

Claims

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

performing multiple programming processes for a plurality of non-volatile storage elements, each of said programming process operates to program at least a subset of said non-volatile storage elements to a set of target conditions using program pulses; and

for at least a subset of said programming processes;

identifying a program pulse associated with achieving a particular result for a respective programming process and using said identified program pulse to adjust programming for a subsequent programming process for said non-volatile storage elements.

2. A method according to claim 1, wherein:

said multiple programming processes includes four programming passes, said four programming process includes a first programming pass, a second programming pass, a third programming pass and a fourth programming pass;

said first programming pass programs said non-volatile storage elements from an erased threshold voltage distribution to a set of two threshold voltage distributions;

said second programming pass programs said non-volatile storage elements from said set of two threshold voltage distributions to a set of four threshold voltage distributions;

said third programming pass programs said non-volatile storage elements from said set of four threshold voltage distributions to a set of eight threshold voltage distributions; and

said four programming pass programs said non-volatile storage elements from said set of eight threshold voltage distributions to a set of sixteen threshold voltage distributions.

3. A method according to claim 1, wherein:

said multiple programming processes includes a soft programming process and a data programming process.

4. A method according to claim 1, wherein:

said particular result is a first non-volatile storage element reaching a predetermined target.

5. A method according to claim 1, wherein:

said particular result is a set of N non-volatile storage elements reaching a predetermined target.

6. A method according to claim 1, wherein:

said using said identified program pulse to adjust programming for a subsequent programming process includes setting an initial magnitude of programming pulses for said subsequent programming process.

7. A method according to claim 1, wherein:

identifying a program pulses associated with achieving a particular result includes identifying a particular pulse that caused a set of one or more non-volatile storage elements to reach a predetermined target; and

said using said identified program pulse to adjust programming for a subsequent programming process includes setting an initial magnitude of programming pulses for said subsequent programming process to be a same magnitude as said particular pulse.

8. A method according to claim 1, wherein:

said multiple programming processes includes a soft programming process and a data programming process;

said method further includes receiving a request to program data; and

said request is received after performing said soft programming process and prior to performing said data programming process.

9. A method according to claim 1, wherein:

said multiple programming processes includes a soft programming process and a data programming process; and

said method further includes storing information about said identified program pulse after said soft programming and accessing said stored information during said data programming process.

10. A method according to claim 1, wherein:

said multiple programming processes includes a soft programming process and a data programming process;

said method further includes storing information about said identified program pulse after said soft programming, performing other programming processes prior to said data programming process and accessing said stored information during said data programming process.

11. A method according to claim 1, wherein:

said multiple programming processes includes four programming passes; and

at least one of said programming passes comprises;

reading an identification of a program pulse from previous programming,

setting an initial magnitude for a programming signal based on said identification of said program pulse from previous programming, and

applying said programming signal.

12. A method according to claim 1, wherein:

said multiple programming processes includes four programming passes; and

at least one of said programming passes comprises;

reading an identification of a program pulse from previous programming,

setting an initial magnitude for a programming signal based on said identification of said program pulse from previous programming,

applying said programming signal,

storing a new identification of a program pulse for a subsequent programming pass if a predetermined number of non-volatile storage elements have reached a particular target.

13. A method according to claim 1, wherein:

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

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

performing multiple programming passes for a plurality of non-volatile storage elements, each of said passes operates to program at least a subset of said non-volatile storage elements to a set of target conditions using program pulses; and

for at least a subset of said programming passes;

identifying a program pulse at which a predetermined number of one or more non-volatile storage elements reach a target threshold voltage and setting an initial magnitude for program pulses used in a subsequent programming pass based on said identified program pulse.

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

performing a first programming process for a plurality of non-volatile storage elements, said first programming process operates to program at least a subset of said non-volatile storage elements to a first set of one or more target conditions using a set of program pulses;

identifying a program pulse of said first programming process at which a predetermined number of one or more non-volatile storage elements reach said first set of one or more target conditions; and

performing a second programming process for said plurality of non-volatile storage elements, said second programming process operates to program at least some of said non-volatile storage elements to a second set of one or more targets using a program pulse signal that has an initial magnitude based on said identified program pulse.

16. A method according to claim 15, wherein:

said first programming process is a soft programming process that is performed with an erase operation;

said second programming process is a data programming process;

said identifying a program pulse includes storing information about said identified program pulse in a non-volatile storage device; and

said performing a second programming process includes reading said information about said identified program pulse from said non-volatile storage device after performing intervening operations between said first programming process and said second programming process.

17. A method according to claim 15, wherein:

said first programming process and said second programming process are data programming processes that program different pages of data in said non-volatile storage elements.

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

erasing a plurality of non-volatile storage elements;

soft programming said plurality of non-volatile storage elements after said erasing, said soft programming includes applying a set of program pulses to control gates of said non-volatile storage elements;

identifying a program pulse for which a predetermined number of said non-volatile storage elements complete said soft programming;

adjusting a data programming process based on said number of programming pulses; and

programming a first subset of said non-volatile storage elements using said adjusted data programming process.

19. A method according to claim 18, wherein:

said adjusting includes setting a magnitude of an initial program pulse for said data programming process.

20. A method according to claim 19, wherein:

said plurality of non-volatile storage elements are a block of NAND flash memory cells; and

said first subset of said non-volatile storage elements are NAND flash memory cells connected to a common word line.

21. A method according to claim 19, wherein:

said data programming process is a multi-pass programming process.