WRITE ABORT DETECTION FOR MULTI-STATE MEMORIES

摘要

Techniques are presented to determine whether a multi-state memory device suffers has a write operation aborted prior to its completion. In an example where all the word lines of a memory block is first programmed to an intermediate level (such as 2 bits per cells) before then being fully written (such as 4 bits per cell), after determining that intermediate programming pass completed, the block is searched using the read level for the highest multi-state to find the last fully programmed word line, after which the next word line is checked with the lowest state's read level to determine whether the full programming had begun on this word line. In an example where each word line is fully written before beginning the next word line of the block, after determining the first erased word line, the preceding word line is checked as the highest state to see if programming completed and, if not, checked at the lowest read level to see if programming began.

主权项

1. A method of operating a non-volatile memory circuit, comprising:
initiating a programming operation on a first block of the non-volatile memory circuit, the non-volatile memory circuit having a plurality of blocks formed according to a NAND type architecture in which memory cells of a block are formed along a plurality of word lines, wherein the memory cells store data in an N-bit per cell, multi-state format in which each word line stores N pages of data, where N is greater than or equal to two, and where the word lines of a block are sequentially written in a write sequence from a first end of the block to a second end thereof with each of the word lines being written from an erased state with N pages of data; aborting the programming operation prior to completion; subsequently performing a determination of a degree to which the first block was written during the programming operation prior to aborting, including:
searching the first block to determine the first word line in the write sequence that is in the erased state;subsequently performing, for the word line in the write sequence preceding the determined first word line to be in the erased state, a first read operation to determine whether the preceding word line is readable for the most programmed of the multi-states;in response to the first read operation determining that the preceding word line is not readable for the most programmed of the multi-states, performing for the preceding word line a second read operation for the least programmed of the multi-states above the erased state; andbased on the second read operation, determining whether programming began on the next word line in the write sequence when the programming operation was aborted.