Forming-free resistive switching of TiOx layers with oxygen injection treatments

In terms of defect generation and redistribution, the electrical forming process and filamentary conduction lead conventional RRAM cells to low yield, high operation current, and large operation variations [1-3]. Recently, emerging RRAM cells based on the redox reaction mechanism were proposed to eliminate electrical forming process [4]. However, the endurance was below few thousands cycles and device reliability still remained issues. Moreover, variations in operation parameters and device characteristics could not be avoided unless complex material engineering and film stacks were conducted [5, 6]. In this work, we fabricated TiN/TiO_x/TiN RRAM cells with a oxygen injection (OI) treatment to place excess oxygen ions into TiO_x films and characterized their forming-free and bi-polar resistive switching. Maximum resistance ratio is above 10⁴ and low set/reset current density is lower than 10 nA/um². The capability of various resistance sates shows highly potential of multi level cell (MLC). Then resistive switching is also discovered by structural and electrical analyses showing the excess oxygen occupations of vacancies in TiO_x layers.