Evolution of phase change memory characteristics with operating cycles: Electrical characterization and physical modeling

摘要

The authors report an improvement in electrical characteristics with operational cycles of phase change memory cells having Ge_2Sb_2Te_5 as the active material. An increase in amorphous-state resistance and threshold voltage and decrease in crystalline-state resistance with cycling are observed, which can be explained by gradual compositional change of the memory material driven by the energy input during programming operations. It is also found that melting of the active volume is critical for such improvement in the electrical characteristics. A physical model is proposed based on an expanding cell active volume with operating cycles to self-consistently explain the reported electrical data.