Evidence for Voltage-Driven Set/Reset Processes in Bipolar Switching RRAM

Understanding the physical mechanisms for resistance change in metal oxides is a key challenge to assess the scalability of resistive-switching random access memory (RRAM) devices. From this standpoint, the time dependence of filament formation and dissolution in metal oxides can provide a useful insight into the fundamental mechanism of resistive switching. In this paper, we show an experimental study of the time-dependent filament growth and of the voltage dependence of set/reset times in HfOx-based RRAM devices. The voltage across the device is shown to be regulated at any given time irrespective of the compliance current and the applied voltage, evidencing that voltage is the controlling parameter for the filament formation and dissolution during switching. These results are explained in terms of a thermally-activated ion migration model for filamentary switching. The model allows for an analytical calculation of the scaling dependence of set/reset times and energies in RRAM.