Drift-resilient cell-state metric for multilevel phase-change memory

A new cell-state metric is proposed for multilevel phase-change memory (PCM) that is more representative of the fundamental programmed entity, i.e., the amorphous/crystalline phase configuration in the PCM cell. This metric exhibits improved performance in terms of drift and better sensing resolution of cell states with a large amorphous-phase fraction when compared to the conventional low-field resistance metric. Experimental results using PCM test devices of mushroom type demonstrate the efficacy of the new metric.