Resistance switching behaviors of hafnium oxide films grown by MOCVD for nonvolatile memory applications

Resistive switching characteristics of hafnium oxide were studied for possible nonvolatile memory device applications. The Hf O2 films were grown by metallorganic chemical vapor deposition (MOCVD) at 400°C using tetrakis(diethylamido)hafnium [Hf (N (C2 H5) 2) 4] as a precursor and oxygen gas as an oxidizing agent. The film was polycrystalline and had gradational compositions of Hf and O atoms. Current-voltage characteristics of the films were investigated with 1 mA compliance. A reproducible resistance switching behavior was observed with high resistance ratio of about 104 - 109, which is higher than other comparable materials, such as Ti O2 and Zr O2. SET and RESET voltages were measured about 0.8 and 1.5 V, respectively, indicating that the device can be operated below 2 V. The devices were operated in ohmic conduction mechanism. During the forming process, characteristics of Schottky emission were observed, which indicates that conduction mechanisms between SET and forming processes are different. The bipolar resistance switching behavior was also observed as well as unipolar resistance switching behavior.