Threshold Shift Observed in Resistive Switching in Metal-Oxide-Semiconductor Transistors and the Effect of Forming Gas Anneal

In this paper the resistive switching mechanism, which is crucial for the operations of RRAM devices, is investigated using HfO2 based MOSFETs. After the SET operation, MOSFETs exhibit a threshold voltage (VT) shift that is found to be closely related to the formation of conductive filaments in the gate oxide. The RESET operation performed through a forming gas anneal treatment is found to have the same effect of applying a reverse polarity gate voltage sweep, as usually done in bipolar switching RRAM devices. After RESET, the gate current and VT measured shift back to their pristine levels, indicating the passivation of oxygen vacancies (forming the conductive path) as the most likely physical mechanism responsible for RRAM’s RESET operation. TEM analysis and physical simulations support these conclusions.