Reduced Threshold Current in NbO2 Selector by Engineering Device Structure

Abstract

Abstract —The leakage current scaling issues for NbO 2 selec-tor devices are investigated. By introducing a rough Pt bot-tom electrode (BE) (RMS roughness ∼ 2.5 nm) and insertinga 20-nm-thick dielectric layer (Nb 2 O 5 and HfO 2 ) between theBE and NbO 2 layer, we show that the threshold current forthe insulator-metal-transition in microscale devices ( ∼ 150 µ m)can be reduced to ∼ 20 µ A, close to that realized in nanoscale( ∼ 10 nm) 3-D vertical ReRAM. This could be attributed to athermal confinement effect caused by the presence of a permanentconductive filament in dielectric layer. The experimental resultsare supported by finite element simulation. Index Terms —Non-volatile memory, resistive switching,threshold switching, niobium oxide, cross-point memory. I. I NTRODUCTION R ECENTLY, hybrid 1 selector + 1 resistor (1S1R) mem-ory devices based on insulator-metal-transition (I-M-T)selectors have been shown to have performance suitable for usein next generation non-volatile memory [1]–[6]. The advan-tage of threshold-switching selector elements is that they canoperate at current densities that are compatible with resistive-switching memory devices under high-voltage operation [2].However, they have the disadvantage that they operate atcurrents in the range 0.1–10 mA in the low voltage regime,much higher than the 1–10