Enhancing phase change memory lifetime through fine-grained current regulation and voltage upscaling

Phase Change Memory (PCM) recently has emerged as a promising memory technology. However it suffers from limited write endurance. Recent studies have shown that the lifetime of PCM cells heavily depends on the RESET energy. Typically, larger than optimal RESET current is employed to accommodate process variation. This leads to over-programming of cells, and dramatically-shortened lifetime. This paper proposes two innovative low power techniques, Fine-Grained Current Regulation (FGCR) and Voltage Upscaling (VU), to cut down the RESET current, leaving a small number of difficult-to-reset cells unused. We then utilize error correction code to rescue those cells. Our experimental results show that FGCR and VU reduce the PCM write power by 33%, and prolong the lifetime of a PCM chip by 71%–102%.