Improvement of Sensing Margin and Reset Switching Fail of RRAM

To develop a high voltage read margin ΔVrd, deep reset engineering and defect engineering are proposed. To realize the defect engineering, the amount of oxygen vacancy of the resistor was controlled by optimizing the material of the reservoir (RSV) and switching oxide. We investigated the barrier height modulation, which was formed by the Ru bottom electrode (BE) having a high work function, to demonstrate the concept of deep reset engineering by reducing the set current (Iset) of the HfO2 resistor (1R) to the turn-on current (Ith) of the selector device (1S). Further, we identified the causes of the negative set fail through the chemical analysis of the HfO2/BE TiN interface to improve the reset switching fail. Unstable TiON and TiOx chemical species, which present in the interface of HfO2/BE TiN, take oxygen from the resistor HfO2 and create the parasitic defect (or filament), which was injected from BE TiN. To improve the negative set fail of RRAM, we proposed the O3 surface treatment of BE TiN at a high temperature (∼320 °C) and the BE Ru with a superior oxidation resistance. By using deep reset engineering, we successfully increased the ΔVrd of 1S1R by more than 0.5 V. We also demonstrated that Ru BE and the O3 surface treatment of BE TiN improved both the reset window and the negative set.