Patent ID: 9218890
Filing Date: 2015-12-22
Classification: G06F,G11C

Abstract:
1. A method of operating a three dimensional nonvolatile NAND memory comprising: applying a first set of read conditions to a first portion of a block to obtain first data; performing Error Correction Code (ECC) decoding of the first data; determining that the first data is uncorrectable by ECC; in response to determining that the first data in the first portion of the block is uncorrectable by ECC, determining whether a larger unit within the three dimensional NAND memory, that is larger than the first portion of the block, is uncorrectable by ECC when read using the first set of read conditions, the larger unit consisting of: a set of strings within the block, the set of strings consisting of fewer than all strings of the block that are selected together by a common select line while other sets of strings within the block remain unselected and isolated by other select lines; if the stored data is uncorrectable by ECC throughout the larger unit, then applying modified read conditions to the first portion of the block to find a second set of read conditions that provide second data that is correctable by ECC; and returning corrected second data and recording the second set of read conditions for subsequent reads of data of the set of strings while continuing to use a default set of read conditions for the other sets of strings within the block.