Simultaneous sensing of multiple wordlines and detection of NAND failures

摘要

Techniques for a post-write read are presented. In an exemplary embodiment, a combined simultaneous sensing of multiple word lines is used in order to identify a problem in one or more of these word lines. That is, sensing voltages are concurrently applied to the control gates of more than one memory cell whose resultant conductance is measured on the same bit line. The combined sensing result is use for measuring certain statistics of the cell voltage distribution (CVD) of multiple word lines and comparing it to the expected value. In case the measured statistics are different than expected, this may indicate that one or more of the sensed word lines may exhibit a failure and more thorough examination of the group of word lines can be performed.

主权项

1. A method of checking for data integrity of a block of a flash memory, wherein the block has a NAND-type architecture and includes a plurality of word lines each storing one or more pages of data, the method comprising:
generating a plurality of N first reference voltages, where all of the first reference voltages are smaller than a pre-determined voltage; performing a first multi-page sensing operation, including
concurrently applying each of the first reference voltages to one of a plurality N selected word lines corresponding to the same set of NAND strings of the block; andconcurrently applying the pre-determined voltage to the non-selected word-lines of the NAND strings to which the selected word lines belong; and determining the data integrity of the block of data based upon the result of the first multi-page sensing operation.