Multi-level memory systems using error control codes

In this paper, the multi-level memory system using error control codes has been proposed. As compared with other approaches for 2/sup m/-level memory cells, our proposal features an effective grouping of several q-level memory cells with q>2/sup m/ in order to create parity bits of error control codes. Therefore, the proposed methodology can enhance both the yield and reliability without area penalty for multilevel memory systems. The BCH (72,64) code of correcting single error is presented for 5-level memory cells. In contrast to 2/sup 2/-level memory cells, our proposal can improve yields from 61.58% to 99.92% for 16 Mbit and make the mass production of 1 Gbit memory practicable under the approximated model for StrataFlash/sup TM/. Since our work was motivated from the use of q-level cells in substitution for 2/sup m/-level cells, not only multi-level flash memory, but also multi-level DRAM systems, can both benefit from our proposed methodology.