Effects of oxygen content and capping metal layer on bipolar switching properties of HfO2-based resistive random access memory devices

The HfO₂ based insulator is promising for resistive random access memory (RRAM). At first in this work, the effects of different oxygen contents in sputtered HfO₂ on resistive switching memory are investigated. It is observed that the oxygen flux rate would strongly affect the LRS/HRS current ratio and operation voltage. The switching behavior can be attributed to oxygen vacancy assisted conduction filament formation and annihilation. Then, the effects of Ti and Zr capping metal layers on RRAM devices with ALD-HfO₂ insulator are studied. Resistive switching behavior, temperature-dependence retention, and cycling endurance are strongly affected by the property of capping metal layer.