Deposition And Its Resisitve Switcing Characteristic Of Vanadium Oxide Films

With the rapid development of information technology and its growing demand for lower consuming power, higher density of memory device, Non volatile Resistive Random Access Memory (RRAM) has been a hotspot of current researches due to its simple structure, low operating voltage, high read/write speed and great scalability. A variety of materials have been reported to show resistive switching characteristics. However, the optimization of materials and the switching mechanism still remain unclear and much fundamental work has to be done. In this paper, we investigate VO_X material as a new candidate for RRAM device, and study the thin film deposition and resistive switching behaviors of VO_X for its outstanding electrical and optical switching speed.VO_X thin films were deposited by reactive sputtering with a vanadium target, Optimization of fabrication procedure; microstructure and electrical resistive switching properties are also discussed. The orientation and surface topography of VO_X film were characterized by advanced measuring tools as XRD and AFM. The electoral resistive properties of the film were obtained by Semiconductor Parameter Analyzer (SPA) and the conducting mechanism of VO_X film was investigated with Conductive AFM. These studies can be exhibited specifically as below.First, optimization in deposition procedure of thin films: impacts on deposition rate, component, crystalline state, topography and initial resistance brought about by oxygen partial pressure, sputtering power, ambient pressure, substrate temperature, annealing temperature and thickness of films were elucidated. The deposition of VO_X films was optimized with a configuration of 20% oxygen content of (Ar+O2) gases, sputtering power of 200W,1Pa working pressure and a 450℃annealing temperature. The in-situ morphologies have obvious changes with the increase of temperature.Secondly, impact on the electrical switching properties of Cu/VO_X/Cu brought about by substrate temperature, sputtering power, annealing time were elucidated. The change trends of Forming,set and reset on different deposition conditions were discussed.Thirdly, the Forming voltage of Cu/VO_X/Cu was 1.63V after annealing, achieve the purpose of lowering the threshold voltage. The Cu/VO_X/Cu unit was the coexistence of unipolar and bipolar resistive switching characteristics.Finally, micro-analysis of (I-V) characteristics of VO_X/Cu were characterized by conductive AFM (CAFM), we can draw a conclusion that the conduction mechanism of Cu/VO_X/Cu was formation and rupture of filaments, which was filament mechanism.