HfOx thin films for resistive memory device by use of atomic layer deposition

The materials properties and resistance switching characteristics of hafnium oxide-based binary oxide were investigated for next generation memory device application. A nonstoichometric hafnium oxide (HfO_x) film with a mixture structure of monoclinic and tetragonal phase and some metallic Hf-Hf bonds on TiN/Si were prepared by atomic layer chemical vapor deposition (ALCVD). Resistance random access memory devices consisting of Pt/HfO_x/TiN/Si with low power operation (< 0.4 mW) and reset current (< 100 μA) were fabricated. The resistance ratio of high resistance state to low resistance state maintains 100-1000 and after 1000 cycles of repetitively switching. A 1-nm-thick Al₂O₃ film in the interface between top electrode and HfO_x films, the Pt/Al₂O₃/HfO _x/TiN/Si memory devices were found that soft-error of set and reset process often occurred. Interface states in the anode side may play an important role in maintaining a stable resistive switching for HfO_x-based memory devices.