Resistive Switching Behavior In Aluminum Oxide Film Grown By Chemical Vapor Deposition

With the development of semiconductor and microelectronic technology, the feature size of integrated circuit is becoming smaller and traditional flash memory has reached its physics limitation. The demand of new and advanced non-volatile memory has grown in these years. Now there are mainly four categories of new non-volatile memory:Ferroelectric Random Access Memory (FRAM), Magnetic Random Access Memory (MRAM), Phase-change Random Access Memory (PRAM) and Resistance Random Access Memory (RRAM). The RRAM attracts significant attention as a promising candidate for next generation nonvolatile random access memories.The mechanism of RRAM is that some material would have different resistant under different electronic stimulation. The advantages of RRAM are small scale, low power consumption, high operation speed, non-volatile and compatible with modern CMOS process. The common resistance switching material is mainly metal oxide:TiO, TiO2, CuOx, ZrO2 and etc. However using Al2O3 as layer of resistance switching has not reported.(1) Al2O3 thin film fabricated by MOCVDIn this paper, Al2O3 thin film was deposited by MOCVD method. Al(AcAc)3 was used as the metal organic source, oxygen as oxidizing material and quartz as the substrate. Two kinds of Al2O3 thin film was deposited which structures are amorphous and polycrystalline separately. The thickness, surface morphology and roughness, chemical element ratio, transmission and electronic of the Al2O3 thin film were characterized by AFM, XPS, ultraviolet-visible-infrared spectroscopy and semiconductor device analyzer. The characterization shows that the film has smooth surface with little roughness and good transmittance of visible light. The xps demonstrated that the thin film is oxygen and aluminum. The IV-t result of electronic measurement also indicates that the deposited Al2O3 film is n-type semiconductor due to metal vacancy.(2) Influence of experiment parameter on crystal qualityIn the experiment, experiment parameters like source evaporation temperature, substrate temperature and oxygen flow affect film crystal quality was studied. In a conclusion, evaporation temperature was kept same as the melting point to keep the deposition of Al2O3 thin film stable. The substrate temperature is the main factor that determine the Al2O3 crystal structure. When the temperature is below 600℃, the crystal of Al2O3 is amorphous, while when the temperature is over 600℃, the crystal of Al2O3 is polycrystalline. The flow of oxygen mainly affect crystal quantity. With the reduction of oxygen flow, the crystal quantity get higher.(3) Resistance switching and mechanism of amorphous and polycrystalline Al2O3In the experiment, amorphous and polycrystalline Al2O3 were used as the resistance switching layer, ITO as the bottom electrode and Ag as the top electrode making a MIM structure. The electronic of the device was characterized by voltage scanning.This two kinds of Al2O3 memristor device show a typical bi-polar memristor switching. However amorphous Al2O3 has a more stable electrical properties. The Vset of amorphous Al2O3 is larger than polycrystalline Al2O3 device. Different kinds of voltage scanning were applied to demonstrate the mechanism of Al2O3 resistance switching phenomenon. In the last we use conductive filament to analyze the phenomenon.