A Zeroing Cell-to-Cell Interference Page Architecture With Temporary LSB Storing and Parallel MSB Program Scheme for MLC NAND Flash Memories

Abstract

A new MLC NAND page architecture is presented as a breakthrough solution for sub-40-nm MLC NAND flash memories and beyond. To reduce cell-to-cell interference which is well known as the most critical scaling barrier for NAND flash memories, a novel page architecture including temporary LSB storing program and parallel MSB program schemes is proposed. A BL voltage modulated ISPP scheme was used as parallel MSB programming in order to reduce cell-to-cell interference caused by the order in which the cells are programmed. By adopting the proposed page architecture, the number of neighbor cells that are programmed after programming a selected cell in BL direction as well as their amount of T/th shift during programming can be suppressed largely without increasing memory array size. Compared to conventional architecture it leads to a reduction of BL-BL cell-to-cell interference by almost 100%, and of WL-WL and diagonal cell-to-cell interferences by 50% at the 60 nm technology node. The proposed architecture enables also to improve average MLC program speed performance by 11% compared with conventional architecture, thanks to its fast LSB program performance.