Improvement of switching uniformity in HfOx-based resistive random access memory with a titanium film and effects of titanium on resistive switching behaviors

In this study, the effects of the Ti layer on resistive switching behaviors of HfOx-based resistive switching random access memory (ReRAM) were investigated. After introducing a thin Ti layer (similar to 10 nm) between the Ta and HfOx layers, both cycle-to-cycle uniformity within one cell and cell-to-cell uniformity were significantly improved. In addition, the higher ON/OFF ratio was obtained owing to the resistance increase in the high-resistance state, and a high device yield (>90%) also was achieved. The improvement of switching uniformity can be explained by the Ti doping effect, which is caused by the diffusion of Ti into the HfOx layer. In addition, the Ti layer had the effect of generating more oxygen vacancies in the HfOx layer, which led to the lowering of forming voltage (similar to 2.6 V). To confirm the change in the amount of oxygen vacancies, X-ray photoelectron spectroscopy analysis was performed. The formation of the TiOx layer and the Ti doping effect are considered to contribute to the generation of more oxygen vacancies in the HfOx layer. (C) 2014 The Japan Society of Applied Physics