Patent ID: 11972812
Assignee: SANDISK TECHNOLOGIES, INC.
Field: Computer technology (Electrical engineering)
Classification: CPC G | IPC G

Claim 17:
18. A method of operating non-volatile memory, comprising:
identifying memory cells connected to the common word line that have had their threshold voltages unintentionally drift lower than programmed, the memory cells are capable of being programmed to a plurality of data states, the plurality of data states includes low data states and a high data state, the low data states include lower threshold voltages than the high data state, the identifying comprises:
performing a first sensing operation to determine whether memory cells have respective threshold voltages above a lower voltage limit, the lower voltage limit is a read compare voltage for a data state less a first offset,
performing a second sensing operation to determine whether memory cells have respective threshold voltages below an upper voltage limit, the upper voltage limit is the read compare voltage for the data state plus a second offset,
determining which memory cells have respective threshold voltages above the lower voltage limit and below the upper voltage limit, and
identifying memory cells that have had their threshold voltages unintentionally drift lower than programmed as the memory cells that were determined to have respective threshold voltages above the lower voltage limit and below the upper voltage limit and have neighbor memory cells on neighbor word lines in one or more low data states; and

performing programming on the memory cells identified to have had their threshold voltages unintentionally drift lower than programmed without performing programming for memory cells that are connected to the common word line that were not identified to have had their threshold voltage unintentionally drift lower than programmed.