Segmented bitscan for verification of programming
View Patent ↗A set non-volatile storage elements are subjected to a programming process in order to store a set of data. During the programming process, one or more verification operations are performed to determine whether the non-volatile storage elements have reached their target condition to store the appropriate data. Decisions about whether to continue programming or whether the programming is successful are made based on whether overlapping groups of the non-volatile storage elements have less than a threshold number of non-volatile storage elements that are not properly programmed.
1. A method for programming non-volatile storage, comprising:
subjecting a set of non-volatile storage elements to programming, said set of non-volatile storage elements includes a plurality of groups of non-volatile storage elements and a set of one or more redundant non-volatile storage elements;
determining how many of said redundant non-volatile storage elements have not reached one or more respective target levels;
determining how many non-volatile storage elements of a first group have not reached one or more respective target levels;
calculating a first sum of said redundant non-volatile storage elements that have not reached one or more respective target levels plus said non-volatile storage elements of said first group that have not reached one or more respective target levels;
comparing said first sum to a first threshold; and
determining whether said set of non-volatile storage elements are properly programmed at least partially based on said comparing said first sum to said first threshold.
2. A method according to claim 1 , further comprising:
determining how many non-volatile storage elements of a second group have not reached one or more respective target levels;
calculating a second sum of said redundant non-volatile storage elements that have not reached one or more respective target levels plus said non-volatile storage elements of said second group that have not reached one or more respective target levels;
comparing said second sum to a second threshold; and
determining whether said set of non-volatile storage elements are properly programmed at least partially based on said comparing said second sum to said second threshold.
3. A method for programming according to claim 2 , wherein:
said first threshold is equal to said second threshold.
4. A method according to claim 1 , wherein:
said determining how many non-volatile storage elements of said first group have not reached one or more respective target levels comprises determining how many non-volatile storage elements of a first portion of said first group have not reached one or more respective target levels and determining how many non-volatile storage elements of a second portion of said first group have not reached one or more respective target levels; and
said first sum is based on said redundant non-volatile storage elements that have not reached one or more respective target levels plus said non-volatile storage elements of said first portion of said first group that have not reached one or more respective target levels plus said non-volatile storage elements of said second portion of said first group that have not reached one or more respective target levels.
5. A method according to claim 4 , further comprising:
determining how many non-volatile storage elements of a second portion of a second group have not reached one or more respective target levels;
calculating a second sum of said redundant non-volatile storage elements that have not reached one or more respective target levels plus said non-volatile storage elements of said second portion of said first group that have not reached one or more respective target levels and said non-volatile storage elements of said first portion of said second group that have not reached one or more respective target levels, said second portion of said first group overlaps with said second group;
comparing said second sum to a second threshold; and
determining whether said set of non-volatile storage elements are properly programmed at least partially based on said comparing said second sum to said second threshold.
6. A method for programming according to claim 5 , wherein:
said first threshold is equal to said second threshold.
7. A method according to claim 5 , further comprising:
subjecting said set non-volatile storage elements to additional programming if said first sum is greater than said first threshold or said second sum is greater than said second threshold; and
stopping said programming process if at least said first sum is less than said first threshold and said second sum is less than said second threshold.
8. A method according to claim 1 , wherein said determining how many non-volatile storage elements of said first group have not reached one or more respective target levels comprises:
(a) performing a binary search on said group to find a first non-volatile storage element that is not properly programmed;
(b) updating a count of non-volatile storage elements that are not properly programmed;
(c) tagging said first non-volatile storage element so that it will not be counted again; and
(d) repeating steps (a), (b) and (c) to determine how many non-volatile storage elements are not properly programmed.
9. A method according to claim 8 , wherein:
said non-volatile storage elements are multi-state flash memory devices.