Evidence of the Prominent Role of the Time-Under-Melt Parameter in the Reset Switching of Phase-Change Line Cells

The resistive-switching phase-change memory (PCM) is gaining increasing interest as a potential flash replacement, mainly due to scalability, faster writing and better endurance. PCM cells are typically programmed to the high- resistive amorphous state using a high current pulse (reset programming), and to the low-resistive crystalline state using a longer pulse of lower amplitude (set programming). The parameters considered to mainly control reset switching are the reset current I_R, sufficiently high to reach the melt temperature T_m of the PCM material, and the quench time t_q, short enough to freeze-in the melt state. The optimization of these parameters, as demonstrated for Ge₂Sb₂Te₅-based vertical cells in the literature (D. Mantagazza et al., 2006), (T. Nirschi et al., 2007), is thus a key to better control the switching of the cell. In the present work the influence of the pulse parameters on the reset state is investigated for a SbTe-based lateral cell. A new phenomenon affecting the resistance of the amorphous phase after reset is identified and a strong influence of the time-under-melt parameter is demonstrated.