Threshold shift observed in resistive switching in metal-oxide- semiconductor transistors and the effect of forming gas anneal

The resistive switching mechanism, which is crucial for the operations of resistive random access memory (RRAM) devices, is investigated using HfO ₂ based MOSFETs. After the SET operation, MOSFETs exhibit a threshold voltage (V _T) 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 V _T 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 RRAMs RESET operation. Transmission electron microscopy analysis and physical simulations support these conclusions.