Data recovery on cluster failures and ECC enhancements with code word interleaving

摘要

Techniques are presented for dealing with errors that arise from cluster fails, where a number of memory cells in the same area fail. An ECC code word can tolerate a given total amount of error while still being able to still be decoded, so that if error due to clusters can be identified and removed or lessened, it may be possible to still decode the word not otherwise decodable. After identifying possible error bit cluster locations, one or more bits in the cluster locations are flipped to see if the data content of the code word can be extracted. For embodiments using LDPC ECC code, uncertainty can be added for the bits of a suspected cluster location. To reduce the effects of cluster failures, code words can be interleaved within a page and the difference code words can have differing levels of ECC capability.

主权项

1. A method of reading data stored in a non-volatile memory array of a memory system, comprising:
reading an ECC (error correction code) code word written in memory cells along a word line of the non-volatile memory array, the ECC code word including a plurality of bits of data and one or more bits of error correction code associated with the data; identifying an area along the word line from which the ECC code word was read that indicates a cluster of errors; altering the value of one or more bits of the ECC code word as read from the identified area; feeding the ECC code word with the altered values to ECC circuitry on the memory system; and determining by the ECC circuitry of whether the ECC code word with the altered values is successfully decoded by the ECC circuitry.