Lowering forming voltage and forming-free behavior of Ta<inf>2</inf>O<inf>5</inf> ReRAM devices

In this paper, we investigate the impact of Ta and Ta 2 O 5 thickness and of thermal treatment for the Ta 2 O 5 layer on the forming and switching characteristics of Pt/Ta 2 O 5 /Ta/Pt ReRAM devices. The forming voltage (V FORM ) decreases with increasing Ta and decreasing Ta 2 O 5 thickness. However, V FORM saturates (~ 2 V) for thicker Ta layers. Thinner Ta 2 O 5 switching layer can further reduce the forming voltage to <; 1 V for 3 nm-thick Ta 2 O 5 . However, thinner Ta 2 O 5 degrades the R OFF / R ON ratio and retention of the ReRAM device. On the other hand, thermal treatment of the Ta 2 O 5 results in decrease of initial resistance and V FORM , and rapid thermal anneal at 600°C in O 2 ambient induces forming-free behavior for 70% of the characterized devices. These forming-free devices show highly reliable switching operation up to 10 6 cycles with R OFF / R ON > 10 and retention time of 10 4 s at 125 °C.