The resistive switching characteristics in tantalum oxide-based RRAM device via combining high-temperature sputtering with plasma oxidation

High-temperature (320°C) sputtering combined with plasma oxidation was employed to form Ta2O5/TaOx bi-layer devices. For comparison, Pt/TaOx/Pt structures, where TaOx layers were reactively sputtered at room temperature and 320°C, respectively, were fabricated. No resistive switching was observed for the devices where TaOx was deposited at room temperature, while a few switching cycles were observed for the devices where TaOx was deposited at 320°C. By combining high-temperature sputtering with plasma oxidation, the Ta2O5/TaOx bi-layer devices exhibited much more and better I-V cycles. The reset current was reduced drastically (20mA→100μA), and the uniformity of device performance was enhanced. Resistance switching of the Ta2O5/TaOx bi-layer devices under voltage pulses was achieved, and Roff/Ron ratio was ∼10. The formation of a large quantity of Ta2O5 was confirmed by X-ray photoelectron spectroscopy after the plasma oxidation. A comparison and analysis of improvement in device performance was conducted. It is demonstrated that combining high-temperature sputtering with plasma oxidation is able to improve resistive switching characteristics, and is an effective and feasible method for reducing reset current and enhancing device stability. The improvement was attributed to formation of Ta2O5 on the surface of the TaOx layer by plasma oxidation.