Read operation for non-volatile storage that includes compensation for coupling

• US 7,321,510 B2
• Filed: 12/27/2006
• Issued: 01/22/2008
• Est. Priority Date: 04/05/2005
• Status: Expired due to Fees

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Chen, Jian, Li, Yan
• Primary Examiner(s): Nguyen; Tuan T.
• Application Number:
  US11/616,764
• Publication Number:
  US 20070103982A1
• Time in Patent Office: 391 Days
• Field of Search: 365/185.1, 365/185.05, 365/185.03
• US Class Current: 365/185.1
• 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 16/3418 Disturbance prevention or evaluation; Refreshing of disturbed memory data
• CPC Class Codes: G11C 16/3422 Circuits or methods to evaluate read or write disturbance in nonvolatile memory, without steps to mitigate the problem

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). The problem occurs most pronouncedly between sets of adjacent memory cells that have been programmed at different times. To compensate for this coupling, the read process for a given memory cell will take into account the programmed state of an adjacent memory cell.

Claims

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

programming a first non-volatile storage elements and a second set of non-volatile storage elements, said first set of non-volatile storage elements and said second set of non-volatile storage elements each store first and second groupings of data, said programming includes writing to a particular non-volatile storage element with respect to said second grouping of data subsequent to writing to adjacent non-volatile storage elements for said first grouping of data;

reading charge information from said second set of non-volatile storage elements; and

performing a read operation on said first set of non-volatile storage elements, said read operation uses a first compensation for non-volatile storage elements of said first set of non-volatile storage elements adjacent to non-volatile storage elements of said second set of non-volatile storage elements that have charge information read which provide a first indication and said read operation does not use said first compensation for non-volatile storage elements of said first set of non-volatile storage elements adjacent to non-volatile storage elements of said second set of non-volatile storage elements that have charge information read which does not provide said first indication.

2. A method according to claim 1, wherein:

said first grouping of data is a lower page and said second grouping of data is an upper page;

said first set of non-volatile storage elements stores lower page 0 and upper page 2; and

said second set of non-volatile storage elements stores lower page 1 and upper page 3.

3. A method according to claim 1, wherein:

said first grouping of data is a first page and said second grouping of data is a second page; and

said first indication indicates that a particular non-volatile storage element of said second set of non-volatile storage elements has its second page programmed.

4. A method according to claim 1, wherein:

said first compensation includes using an offset voltage to a normal read compare voltage applied to a word line connected to said first set of non-volatile storage elements.

5. A method according to claim 1, wherein:

said first compensation includes connecting a capacitor to a sense amplifier.

6. A method according to claim 1, wherein:

said first compensation includes reducing a source line bias.

7. A method according to claim 1, wherein:

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