Asymmetric structure with high electric-thermal conversion efficiency for nanoscale phase change memory based on three-dimensional simulation

How to decrease the reset current is a key point for improving the performance of phase change memory (PCM). Therefore, an asymmetric structure of PCM is proposed to achieve this aim. Using ANSYS, three-dimensional finite element models were established to simulate the efficiency of electric-thermal conversion in PCM cells with an asymmetric structure and a conventional symmetric structure. Simulation results show that the peak temperature in the asymmetric cell with a feature size (FS) of 16 nm is higher than that in the conventional symmetric cell with the same FS by 37.2% when the same current pulse is applied. In an asymmetric cell, the current path and heat dissipating conditions are quite different from those in a symmetric cell, which leads to the remarkable enhancement in electric-thermal conversion efficiency. Simulation results also suggest a proper offset value in asymmetric structures, with which the efficiency of electric-thermal conversion can be further improved. If this new structure is used in fabrication, no additional cost will be incurred because the only difference between symmetric and asymmetric structures is the position of the top opening of the electrodes, indicating that the new structure is highly compatible with modern fabrication processes of PCM.