Block level grading for reliability and yield improvement

摘要

A system for grading blocks may be used to improve memory usage. Blocks of memory, such as on a flash card, may be graded on a sliding scale that may identify a level of “goodness” or a level of “badness” for each block rather than a binary good or bad identification. This grading system may utilize at least three tiers of grades which may improve efficiency by better utilizing each block based on the individual grades for each block. The block leveling grading system may be used for optimizing the competing needs of minimizing yield loss while minimizing testing defect escapes.

主权项

1. A flash memory device comprising:
a non-volatile storage having an array of memory blocks storing data; and a controller in communication with the non-volatile storage, wherein the controller is configured to:
test at least a portion of the memory blocks;grade the tested memory block by assigning each of the tested blocks one of at least three grades; andrestrict usage for some of the memory blocks based on the grade for those memory blocks.