Compensating for coupling in non-volatile storage
AssigneeSanDisk Corporation
InventorsJian Chen, Raul-Adrian Cernea, Gerrit Jan Hemink
Life of this patent
Estimating the term…
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.
Claims20
A method for reading data from a first set of non-volatile storage elements storing data for at least a first page and a second page, comprising:
- determining charge level data for a second set of non-volatile storage elements adjacent to said first set of non-volatile storage elements, said first set of non-volatile storage elements and said second set of non-volatile storage elements associated with at least four data states;
- and
- performing multiple read operations using different reference levels distinguishing between two adjacent data states and, for each of said first set of non-volatile storage elements, choosing to record information associated with one of said read operations based on charge level data for a respective adjacent non-volatile storage element of said second set of multi-state non-volatile storage elements, said recorded information indicates data values for said first page of data.
A method for reading data from a first set of non-volatile storage elements storing data for at least a first page and a second page, comprising:
- determining charge level data for a second set of non-volatile storage elements adjacent to said first set of non-volatile storage elements, said first set of non-volatile storage elements and said second set of non-volatile storage elements associated with at least four data states;
- reading first data using a reference associated with a first set of two adjacent data states;
- reading second data using multiple references associated with a second set of two adjacent data states and, for each of said first set of non-volatile storage elements, choosing information associated with one of said multiple references based on charge level data for a respective adjacent non-volatile storage element of said second set of multi-state non-volatile storage elements, said first data and said second data in combination indicate data values for said first page of data.
A method for reading data from a first set of multi-state non-volatile storage elements storing data for at least a first grouping and a second grouping, comprising:
- determining charge level data for a second set of multi-state non-volatile storage elements adjacent to said first set of multi-state non-volatile storage elements;
- performing multiple read processes relative to a first reference value for distinguishing threshold voltages relative to two adjacent data states for said first set of non-volatile storage element, each read process uses a different one of a predetermined set of offsets with said first reference value, each of at least a subset of said first set of non-volatile storage element provides final data from an appropriate one of said read processes corresponding to one offset that is associated with a respective adjacent non-volatile storage element;
- and
- determining data values for said first grouping based on said final data, without using other data from user data read processes based on non-zero offsets to reference values between other pairs of adjacent data states.
Dependencies are inferred from the claim text.