Study Of Resistive Memory Effects And Mechanism For Metal Oxide

The current mainstream non-volatile Flash memory is facing a bottleneck for size can not continue to shrink, due to the limitations of its structure. Therefore, it becomes a top priority research to explore the next generation of superior performance non-volatile memory. In recent years, one based on material resistance switching to realize storage called resistance random access memory (RRAM) has been appeared which is expected to become the leader of next generation non-volatile flash memory. RRAM has simple structure, high speed, high density, and compatible with CMOS structures. Although RRAM has so many pretty advantages and attracts many researchers to study, but until now, the mechanism of RRAM is not yet well unified. Thus, it is meaningful for us to have a deeper study of RRAM. Among the materials with the characteristics of resistance, binary metal oxide gets a research focus because of its simple elements, stable property.This paper mainly studied binary metal oxide SnOx and HfOx which with wide band gap. HfOx thin film was deposited by RF sputtering HfO2target on the ITO conductive glass to make the Al/HfOx/ITO devices. We programmed six kinds of oxygen partial pressures from10.0%to50.0%and five kinds of substrate temperatures from300K to700K. Studies had shown that the ratio of high resistance and low resistance can reach more than103when the oxygen partial pressure was20%and the substrate temperatures was500K. This phenomenon can be attributed to partial crystallization of the thin film. The crystallization temperature was so lower, for the particles carrying part of the energy which would contribute to the substrate. The film can occur better crystallization everr though the add temperature was not high. Resistive switching behavior of the HfOx film can be explained by the charge capture process. Through analyzing Ⅰ-Ⅴ curve of the devices, the resistance switching of HfOx film fitted the SCLC mechanism. At the linear region, the current and voltage was proportional relationship; at the nonlinear region, the current and voltage was proportional to the square. The resistance switching model explained the resistance switching behavior by traps capture and release electron on the film. Thin films prepared by RF sputtering HfO2target have poor stability and weak rewritable, probably due to the thin films had more defects and grain boundaries. Latter, we used RF reactive sputtering to prepare SnOx thin films to improve the stability of switching behavior, including the influence of annealing on the film and the impact of the low testing temperature on the electrical properties of the film so on. Studies had shown that thin film devices had a better rewritable capability by RF reaction sputtering. The devices could be switched over100cycles without degradation, which indicated a good endurance. The thin film device had a higher ratio of high resistance and low resistance when dealing with atmospheric annealing and the thin film became in low resistance state at initial state, since the crystallization of the thin film. The resistive switching Ⅰ-Ⅴ characteristics at120-300K were investigated. Leakage current of the thin film device decreased gradually as the temperature decreases. But the threshold voltage (VSET) increased with temperature decreasing. Ⅰ-Ⅴ characteristic curve showed the resistance mechanism of the device was conductive filaments model. In this model, the atoms in the film was decomposed to produce ions and vacancy cause the formation of the conductive channel.