Statistics of set transition in phase change memory (PCM) arrays

This work presents a statistical characterization of the set operation in phase change memory (PCM) arrays. The set performance was studied in devices programmed with increasing size of the amorphous region by means of suitable reset pulses. The thickness-dependent set time and statistics are explained by the different roles of the nucleation and growth of crystalline grains in the amorphous volume. We then analyzed the set transition kinetics comparing 2 set techniques, namely: i) crystallization in the solid state through rectangular pulses below the reset level and ii) crystallization from the liquid phase through triangular pulses above the reset level. The experimental results provide guiding rules for minimizing the energy consumption and the switching variability in PCM arrays.