Study of geometric effect on phase change random access memory

In this paper, phase change random access memory (PCRAM) devices with two different geometric configurations were studied. The geometry effect on device functionalities in terms of thermal and electrical properties has been analyzed by simulation and experiments. Based on 0.35mum technology, 128 bits PCRAM array integrating with CMOS as the selection device were fabricated. The two types of PCRAM cells were implemented and characterized. The simulation results showed that both the bottom electrode and phase change layer geometry and the size of the interface between the phase change material and the bottom electrode were the determinant factors to the temperature profile and heat distribution. Both simulation and experimental results show that PCRAM device with type II structure required lower current to start phase change from crystalline state to amorphous state. However, it required a larger current to be fully RESET. A model was proposed in this paper to discuss this phenomenon