Leakage Current-Forming Voltage Relation and Oxygen Gettering in HfOx RRAM Devices

We observe a trend between initial leakage currents in polycrystalline HfO_x resisitive random access memory (RRAM) cells (before forming) and the forming voltages. This trend points to the dominant role played by conduction paths located at grain boundaries, which is promoted by the oxygen deficiency in HfO_x. One of these paths is then converted into the conductive filament responsible for nonvolatile resistance switching. In addition, we find that by engineering the RRAM stack, the forming voltage can be tuned-up to meet specific RRAM requirements, such as lower power and forming-less operations.