Neighbor-Cell Assisted Error Correction for MLC NAND Flash Memories

Continued scaling of NAND flash memory to smaller process technology nodes decreases its reliability, necessitating more sophisticated mechanisms to correctly read stored data values. To distinguish between different potential stored values, conventional techniques to read data from flash memory employ a single set of reference voltage values, which are determined based on the overall threshold voltage distribution of flash cells. Unfortunately, the phenomenon of program interference, in which a cell's threshold voltage unintentionally changes when a neighboring cell is programmed, makes this conventional approach increasingly inaccurate in determining the values of cells. This paper makes the new empirical observation that identifying the value stored in the immediate-neighbor cell makes it easier to determine the data value stored in the cell that is being read. W