Research On Processing And Dielectric Properties Of Surface Films On Insulating Metallic Substrates

Three kinds of different methods, namely anode oxidation, micro-arc oxidation and DC reactive magnetron sputtering, were employed to treat aluminum substrate which is used for power electronic devices in order to get an insulating surface by form a layer of aluminum nitride (AlN) or aluminum oxide (Al2O3) film. The chemical composition and microstructures of the insulating thin films prepared by different methods were analyzed by X-ray Diffraction (XRD) and Scanning Electron Micrograph (SEM); other properties such as electric resistance, the breakdown field strength and dielectric properties were evaluated using high resistance meter, voltage resistance meter and precision impedance analyzer respectively. The influences of the reactive magnetron sputtering processing condition (sputtering power, distance between the target and the substrate, temperature of the substrate) on the dielectric properties of the experimentally got AlN films were analyzed. Experimental results show: i) in the anode oxidation, using a oxalic acid solution of 2% concentration as the electrolyte, and under the oxidation condition of a constant electrical current of 0.5A and a controlled temperature(<32.5°C), the electric resistance the oxide films of the aluminum reaches as high as 2.34×1013??cm, the breakdown field strength is 73.8 V/μm, and a excellent low frequency (<2MHz) dielectric property (8.75 of the dielectric constant and dielectric lose below 0.20 ) is obtained; ii) the existence of discharge passageway of micro-arc oxidation, so the electric insulation property and the dielectric property of the oxide film were deteriorate; iii) in DC reactive magnetron sputtering, when the sputtering power is fixed at 150W and the distance between the target and the substrate fixed at 5cm, a elevated temperature of substrate resulted in a better thin film of AlN more slippery and with lesser defects, also, the dielectric property is better(ε<1.80,tanδ<0.04, at 200℃); when distance between the target and the substrate is higher, the thin AlN film is better in uniformity and is more slippery, increasing the distance between the target and the substrate is a good way to improve the low frequency dielectric property of the film; by increasing the distance between the target and the substrate from 5cm to 8cm (the sputtering power fixed at 150W), the dielectric reached 4.5 and the...