Study On Composition And Properties Of Silicon Nitride Thin Films Deposited By Mid-frequency Magnetron Sputtering

Thin films of silicon nitride have attracted much interest for their remarkable properties such as high thermal stability, chemical inertness, good dielectric properties. All these properties make it a suitable candidate material for many various technological areas, especially in the fabrication of microelectronic devices as oxidation masks, gate dielectrics, interlevel insulators, final passivation layers and antireflection coating.Silicon nitride thin films have been deposited onto the silicon (001) substrate by a mid-frequency dual-target unbalanced magnetron sputtering of two pure Si targets using different gas (Ar,N2) mixture at fixed other conditions. The properties of microstructure, morphology, thickness and index of refractory of silicon nitride thin films were investigated by fourier transform infrared spectroscopy(FTIR), X-ray diffractometry(XRD), atomic force microscopic(AFM) and ellipse-polarize spectrophotometer. FTIR spectra of the films reveal that the main absorption band of the Si-N bond shifts to higher wavenumbers with decreasing nitrogen matter flow ratio. All the films are amorphous silicon nitride. The surface morphology, index of refractory and deposition rate are found to depend distinctively upon the different nitrogen matter flow ratio. The hardness and Young's modulus values of the films approach approximately 22GPa and 220GPa, respectively.Magnesium (Mg) alloys have attracted much interest for their low density, high specific strength and rigidity, good heat and electrical conductivity. However, the poor corrosion resistance and mechanical properties of Mg alloys limit the advantages of their performance. Therefore, by taking the surface modification technology, the improvement of the chemical and mechanical properties of Mg alloys has the important practical significance.In this dissertation, silicon nitride thin films are deposited on AZ31 magnesium alloys by mid-frequency dual-target magnetron sputtering method. The mechanical properties and corrosion resistance of the silicon nitride thin film were measured to analyze the effect of the surface modification of the SiNx films for the AZ31 magnesium alloys substrate. It was found that the silicon nitride films effectively enhanced the mechanical properties and corrosion resistance of AZ31 magnesium alloys. The corrosion current density was markedly decreased in three orders of magnitude. There was strong and stable interfacial adhesion between the film and the substrate. The microhardness of the AZ31 magnesium alloys increased prominently.