Study On Structure And Optical Properties Of Silicon Dioxide Thin Films Deposited By Mid-frequency Magnetron Sputtering

Silicon dioxide thin film is an ideal optical material for its low refractive index, low extinction coefficient, strong adhesion and high transmission in the visible and near-infrared region, So the SiO2thin film is widely used in microelectronics, optics and other fields. In addition, the silicon dioxide films is widely used in the semiconductor, machinery and other fields for its hardness, wear resistance, good insulation, corrosion resistance and other mechanical properties. In recent years, with the rapid development of flat panel displays and solar cells, silicon dioxide film, which has a lower extinction coefficient and a more stable refractive index and has the characteristics of high resistance, strong adhesion, smooth surface, is required as a buffer layer.The methods of preparing silicon dioxide are mainly thermal oxidation method, electron beam evaporation method, sol-gel method, and the like. These conventional methods for preparing the film, which have their disadvantages and are difficult to overcome, are applied to the field of optics. Magnetron sputtering, which has the characteristics of low deposition temperature, good compactness, large area deposition, etc., holds unique advantages in the deposition of an optical film. In this thesis, MF magnetron sputtering, which has an annealing of the sample, is used to prepare silicon dioxide film. The experiments tries to study oxygen partial pressure, sputtering power and annealing treatment’s effects upon the structure and performance of the film through a large number of tests and a variety of detection methods. Test results show that SiO2films prepared by MF magnetron sputtering are amorphous. With the increase of oxygen partial pressure, the overall deposition rate of films are downward, the surface morphology tends to smooth, roughness of the mean square root is reduced, refractive index and extinction coefficients are significantly reduced. When the oxygen partial pressure is higher than15%, the refractive index of film at a wavelength of600nm are about1.45to1.6and the extinction coefficient is less than10-4. With the increase of the sputtering power, the deposition rate are of linear increase, roughness of the surface mean square root goes up. When the sputtering power is of2.8kW, it significantly increased up to2.26nm; refractive index and extinction coefficient are slightly reduced; when the sputtering power are of0.8kw to2.8kW, refractive index of the thin film at a wavelength of600nm are increased from1.45to1.5. The test results after annealing show that annealing temperature and time has a significant impact on the structure and optical properties of the SiO2film. The annealing treatment procures an adjustment of the thin film structure and the formation of Si-Si bond in the silicon oxide film, the formation of Si-Si chemical bonds directly influences the increase of the refractive index and extinction coefficient.The experiments show that the method of MF magnetron sputtering can be used to prepare silicon dioxide film as a buffer layer, considering such factors as corrosion, surface roughness of the film and the adhesion of film/substrate. The best process parameters for this experiment are:constant current mode I=2.5A (sputtering power P=2.0kW), the oxygen flow rate of30seem, an argon flow of170seem and the sputtering pressure of0.6Pa.