Product Code Schemes for Error Correction in MLC NAND Flash Memories

Error control coding (ECC) is essential for correcting soft errors in Flash memories. In this paper we propose use of product code based schemes to support higher error correction capability. Specifically, we propose product codes which use Reed-Solomon (RS) codes along rows and Hamming codes along columns and have reduced hardware overhead. Simulation results show that product codes can achieve better performance compared to both Bose-Chaudhuri-Hocquenghem codes and plain RS codes with less area and low latency. We also propose a flexible product code based ECC scheme that migrates to a stronger ECC scheme when the numbers of errors due to increased program/erase cycles increases. While these schemes have slightly larger latency and require additional parity bit storage, they provide an easy mechanism to increase the lifetime of the Flash memory devices.