Modeling of Phase-Change Memory: Nucleation, Growth, and Amorphization Dynamics During Set and Reset: Part II-Discrete Grains

We extend our finite-element model of nucleation, growth, and amorphization in phase-change memory devices to model discrete nucleation and grain boundaries, including the evolution of grains within fully crystalline material during long-term anneals. Electrothermal simulations of set and reset operations include a heat of crystallization model and an Arrhenius expression modeling thermionic emission at grain boundaries. Our simulations capture cycle-to-cycle variations due to stochastic nucleation and the interplay of crystallization, the formation of percolation paths, and thermal runaway.