Reliable MLC data storage and retention in phase-change memory after endurance cycling

For phase-change memory to be considered a true universal memory it would have to combine MLC storage, for low cost per bit, with adequately high endurance and at least moderate data retention. However, this appears to be particularly difficult to achieve, because of phenomena such as material segregation, which comes as an effect of cycling, and resistance drift, which is inherent in the amorphous phase and affects the stability of stored data. We present a combination of a memory cell with stable programming behavior over cycling, electrical sensing techniques and signal processing technologies, to demonstrate the viability of reliable, non-volatile, MLC storage in phase-change memory cells after extended endurance cycling.