System for verifying non-volatile storage using different voltages

• US 7,457,163 B2
• Filed: 06/01/2006
• Issued: 11/25/2008
• Est. Priority Date: 06/01/2006
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Hemink, Gerrit Jan
• Primary Examiner(s): Pham; Ly D
• Application Number:
  US11/421,682
• Publication Number:
  US 20070279985A1
• Time in Patent Office: 908 Days
• Field of Search: 365/185.18, 365/185.21, 365/185.22, 365/185.24, 365/185.11
• US Class Current: 365/185.22
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output 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

Abstract

When performing a data sensing operation, including a verify operation during programming of non-volatile storage elements (or, in some cases, during a read operation after programming), a first voltage is used for unselected word lines that have been subjected to a programming operation and a second voltage is used for unselected word lines that have not been subjected to a programming operation. In some embodiments, the second voltage is lower than the first voltage.

Claims

1. A non-volatile storage system, comprising:

a group of connected non-volatile storage elements; and

a managing circuit in communication with said group of connected non-volatile storage elements, said managing circuit applies a particular voltage to a particular non-volatile storage element of said group, while applying said particular voltage to said particular non-volatile storage element said managing circuit applies a first voltage to a first set of one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes since a last erase of said group and a second voltage to a second set of two or more non-volatile storage elements of said group that have not been subjected to a programming process since erasing said group, said managing circuit senses a condition related to said particular non-volatile storage element and said particular voltage as part of a verify operation during a programming processes for said particular non-volatile storage element, said managing circuit performs a read process after said programming process, said read process includes said managing circuit applying a voltage other then said first voltage to said first set of one or more non-volatile storage elements or applying a voltage other then said second voltage to said second set of one or more non-volatile storage elements.

2. A non-volatile storage system according to claim 1, wherein:

said second voltage is lower than said first voltage.

3. A non-volatile storage system according to claim 1, wherein:

said group of connected non-volatile storage elements are NAND flash memory devices that are part of a common NAND string.

4. A non-volatile storage system according to claim 3, wherein:

said first voltage is sufficiently high enough to turn on said one or more non-volatile storage elements of said group that have already been subjected to one or more programming process;

said second voltage is sufficiently high enough to turn on said one or more non-volatile storage elements of said group that have not been subjected to a programming process; and

said second voltage is lower than said first voltage.

5. A non-volatile storage system according to claim 4, wherein:

said managing circuit applies a third voltage to a non-volatile storage element that is a neighbor of said particular non-volatile storage element.

6. A non-volatile storage system according to claim 4, wherein:

said one or more non-volatile storage elements of said group that have already been subjected to one or more programming process are on a source side of said particular non-volatile storage element; and

said non-volatile storage elements of said group that have not been subjected to a programming process are on a drain side of said particular non-volatile storage element.

8. A non-volatile storage system according to claim 1, wherein:

said managing circuit includes any one or a combination of a controller, a state machine, command circuits, control circuits and decoders.

7. A non-volatile storage system, comprising:

a group of connected non-volatile storage elements; and

a managing circuit in communication with said group of connected non-volatile storage elements, said managing circuit applies a particular voltage to a particular non-volatile storage element of said group, while applying said particular voltage to said particular non-volatile storage element said managing circuit applies a first voltage to one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes since a last erase of said group and a second voltage to two or more non-volatile storage elements of said group that have not been subjected to a programming process since erasing said group, said managing circuit senses a condition related to said particular non-volatile storage element and said particular voltage, a first subset of said one or more non-volatile storage elements of said group that have already been subjected to one or more programming process are on a first side of said particular non-volatile storage element, a second subset of said one or more non-volatile storage elements of said group that have already been subjected to one or more programming process are on a second side of said particular non-volatile storage element, and said non-volatile storage elements of said group that have not been subjected to a programming process are on said second side of said particular non-volatile storage element.

9. A non-volatile storage system, comprising:

a group of connected non-volatile storage elements; and

a managing circuit in communication with said group of connected non-volatile storage elements, said managing circuit applies a particular voltage to a particular non-volatile storage element of said group, while applying said particular voltage to said particular non-volatile storage element said managing circuit applies a first voltage to one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes since a last erase of said group and a second voltage to two or more non-volatile storage elements of said group that have not been subjected to a programming process since erasing said group, said managing circuit senses a condition related to said particular non-volatile storage element and said particular voltage, said sensing a condition is performed as part of a verify process while programming said particular non-volatile storage element, said managing circuit performs a read process for said particular non-volatile storage element after said programming, said read process is performed by said managing circuit by applying a common control gate voltage to said one or more non-volatile storage elements of said group and to said two or more non-volatile storage elements of said group.

10. A non-volatile storage system, comprising:

a group of connected non-volatile storage elements; and

a managing circuit in communication with said group of connected non-volatile storage elements, said managing circuit applies a particular voltage to a particular non-volatile storage element of a group of connected non-volatile storage elements, said managing circuit applies a first voltage to one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes since a last relevant erase, said first voltage is applied in coordination with said particular voltage, said managing circuit applies a second voltage to one or more non-volatile storage elements of said group that have not already been subjected to a programming process since said last relevant erase, said second voltage is applied in coordination with said particular voltage, said managing circuit applies a third voltage to a non-volatile storage element that is a neighbor of said particular non-volatile storage element, said third voltage is applied in coordination with said particular voltage, said managing circuit senses a condition related to said particular non-volatile storage element and said particular voltage.

11. A non-volatile storage system according to claim 10, wherein:

said particular voltage is a verify reference voltage;

said first voltage is sufficiently high enough to turn on said one or more non-volatile storage elements of said group that have already been subjected to one or more programming process;

said second voltage is sufficiently high enough to turn on said one or more non-volatile storage elements of said group that have not already been subjected to a programming process;

said third voltage is sufficiently high enough to turn on said neighbor;

said second voltage is lower than said first voltage; and

said sensing a condition is part of a verify operation performed by said managing circuit during programming.

12. A non-volatile storage system according to claim 11, wherein:

said group of connected non-volatile storage elements are NAND flash memory devices that are part of a common NAND string.

13. A non-volatile storage system according to claim 10, wherein:

said one or more non-volatile storage elements of said group that have already been subjected to one or more programming processes are on a source side of said particular non-volatile storage element;

said one or more non-volatile storage elements of said group that have not already been subjected to a programming processes are on a drain side of said particular non-volatile storage element; and

said non-volatile storage element that is said neighbor of said particular non-volatile storage element is on said drain side of said particular non-volatile storage element.