System that compensates for coupling based on sensing a neighbor using coupling

• US 7,602,647 B2
• Filed: 09/08/2008
• Issued: 10/13/2009
• Est. Priority Date: 07/20/2006
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Li, Yan, Fong, Yupin
• Primary Examiner(s): Ho; Hoai V
• Assistant Examiner(s): Lappas; Jason
• Application Number:
  US12/205,918
• Publication Number:
  US 20090003052A1
• Time in Patent Office: 400 Days
• Field of Search: 365/185.17, 365/185.02, 365/185.26, 365/183
• US Class Current: 365/185.18
• 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 16/3427 Circuits or methods to prevent or reduce disturbance of the state of a memory cell when neighbouring cells are read or written
• CPC Class Codes: G11C 16/3454 Arrangements for verifying correct programming or for detecting overprogrammed cells

Abstract

Shifts in the apparent charge stored on a floating gate (or other charge storing element) of a non-volatile memory cell can occur because of the coupling of an electric field based on the charge stored in adjacent floating gates (or other adjacent charge storing elements). To compensate for this coupling, the read or programming process for a given memory cell can take into account the programmed state of an adjacent memory cell. To determine whether compensation is needed, a process can be performed that includes sensing information about the programmed state of an adjacent memory cell (e.g., on an adjacent bit line or other location).

Claims

1. A non-volatile storage system, comprising:

non-volatile storage elements;

control lines in communication with said non-volatile storage elements; and

a managing circuit in communication with said non-volatile storage elements and said control lines, said managing circuit senses a condition of a neighbor non-volatile storage element based on capacitive coupling between a particular control line for a particular non-volatile storage element and a neighbor control line for said neighbor non-volatile storage element, said managing circuit reads information from said particular non-volatile storage element while compensating for coupling between said neighbor non-volatile storage element and said particular non-volatile storage element if said sensed condition is a first condition.

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

said first condition corresponds to a highest programmed state of three or more programmed states and an erased state; and

said particular non-volatile storage element is in a first programmed state.

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

said first condition corresponds to a highest programmed state of three or more programmed states; and

said managing circuit reads information from said particular non-volatile storage element while compensating for coupling between said neighbor non-volatile storage element and said particular non-volatile storage element if said sensed condition is said first condition and said particular non-volatile storage element is in a first programmed state.

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

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

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

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