A New Comprehensive Model of a Phase Change Memory (PCM) Cell

This paper presents a HSPICE macromodel of a phase change memory (PCM) cell. The proposed PCM macromodel consists of two interrelated models, i.e., the operational model and the drift model. The operational model simulates the holding voltage, the programming process, and the continuous change behavior of the PCM resistance (as corresponding to the amorphous and crystalline phases) by considering also the temperature profile and the crystalline fraction. Using these features, drift behaviors are assessed for the resistance and the threshold voltage; the parameter drifts occur when the cell is not been programmed, thus matching simulation with the operational characteristics observed experimentally in a PCM cell. An analysis of the drift behaviors is then presented. This analysis provides the basis by which an electrical-based framework can be used for simulation. The simulation results show that the plots of resistance and threshold voltage of the PCM cell during the modeled drift behaviors are very close to the experimental results. Moreover, selection of the parameters is based on PCM operational features, so the electrical characterization of the drift is simple, easy to simulate and intuitive.