A Compact Phase Change Memory Model With Dynamic State Variables

A SPICE model for phase change memories (PCM) without relying on macro modules is developed in this work. The crystal fraction, physical geometry, and the conduction path of the amorphous region are treated as dynamic state variables to keep track of the memory cell status during SET and RESET. The memory cell resistance is calculated based on a detail 3-D resistance model to capture its transitional behavior during switching. The detail physical formulation correctly reproduced a recent observation of oscillation during the SET operation. The model has been implemented in SPICE, and the convergence of the model is demonstrated by simulations of a complete PCM array. The use of dynamic state variables also significantly reduces the number of internal nodes to one, which helps convergence and reduces the simulation time.