Reduced Threshold Current in NbO2 Selector by Engineering Device Structure

The leakage current scaling issues for NbO2 selector devices are investigated. By introducing a rough Pt bottom electrode (BE) (RMS roughness similar to 2.5 nm) and inserting a 20-nm-thick dielectric layer (Nb2O5 and HfO2) between the BE and NbO2 layer, we show that the threshold current for the insulator-metal-transition in microscale devices (similar to 150 mu m) can be reduced to similar to 20 mu A, close to that realized in nanoscale (similar to 10 nm) 3-D vertical ReRAM. This could be attributed to a thermal confinement effect caused by the presence of a permanent conductive filament in dielectric layer. The experimental results are supported by finite element simulation.