The Preparation And Study Of In-ga-zn-o(IGZO) Thin Film

ITO (indium-tin oxide) thin film is the most widely used one of transparent conductive oxide films in industry, such as in display and solar cell production. It naturally combines the high conductivity and transparence.Indium, as a rare element in earth, probably limits the future application, so scientists have to be looking for the alternative. A series of doped ZnO thin films become the most promising candidates of the ITO films with their outstanding performance. In this article, high-density IGZO target was prepared using Low content of indium and gallium co-doped ZnO powders. A series of IGZO thin films were deposited using RF magnetron sputtering method with different conditions(ie. substrate temperature, sputtering time, sputtering power, distance between target and substrate, sputtering pressure). The films were characterized by X-ray diffraction(XRD), Scanning Electron Microscopy(SEM), Hall-effect device and Ultraviolet-visible light Spectrometer(UV-vis spectrometer). The influences of sputtering parameters on the phase structure, morphology and photoelectric properties of IGZO films were studied. The main conclusions were listed:The structure and surface morphology of IGZO thin films were much influenced by the substrate temperature. The strongest diffraction peak of the XRD patterns changed from (100) to (002) and then transformed into (103) with increasing substrate temperature. As observed by SEM the morphology of the films deposited under different substrate temperature were conical island structure. When the substrate temperature rose from 150℃to 350℃, the island structures became more obvious. The boundaries of islands gradually became blurred till completely disappeared. Obviously that the roughness of the film decreased when the substrate temperature exceeded 400℃. With the increasement of sputtering time and power in a certain range, the crystallization of the films were improved and the size of single island became larger. Adjusting the sputtering pressure and the target-substrate distance, the resistivity decreased at first, then increased. Extending the sputtering time made the resistivity decreased. With further experimentals, we found that the varieties of the film resistivity originates from the carrier concentration and carrier mobility. The best conductivity was obtained with the 55 mm target-substrate distance, 0.5Pa sputtering pressure, 20 min sputtering time, 200W sputtering power and 450℃substrate temperature. IGZO film had the lowest resistivity of 6.83×10^-4Ω·cm, with a carrier concentration of 2.44×10²⁰cm^-3and a Hall mobility of 37.5cm2V^-1S^-1.With the distance between target and substrate and sputtering pressure increasing, the films' average visible transmittance increased at first, and then decreased. The films' average visible transmittance decreased with the sputtering time and sputtering power increasing. With the increasement of the substrate temperature, we did not observe obvious changes of the average visible transmittance of the films. Only above 350℃, the transmittance improved because of better crystallization and lower roughness. The highest average visible transmittance of 76.45% was obtained with the 55mm target-substrate distance, 0.5Pa sputtering pressure, 20min sputtering time, 200W sputtering power and 300℃substrate temperature.