Abstract
Thin film spinning coating of silicon dioxide onsilicon wafer by SiO2 solution prepared through the sol-gel method was investigated. In order to alleviate cracking in making thick film, a method to reduce the capillary force by extractry the solvent from gel through CO2 supercritical fluid was studied. Furthermore, casting process was proceeded by introducing the solution into a mold which made by lithography method, a long waveguide was fabricated after drying and annealing.In this experiment, the SiO2 solution is prepared through the hydrolysis-condensation processes of TEOS with adding acid. The solution is then diluted by ethanol until the viscosity of the solution is suitable for spin coating. SiO2 thin film formed when the solution was geled. Measurements on light absorption, thickness, refractive index, k value coefficent and FTIR were made. The results are helpful to evaluate the feasibility of the fabricated thin film on waveguide device application.In this study, a film with low OH content and 90% transparency can be obtained. The film has a absorption value(k) lower than 0.001 and a refractive index of 1.422(for 1.5mm).Thickness of the film is about 0.5mm, the supercritical extracting method can effectively prevent cracking for forming relative thick film up to 1mm. Furthermore, a waveguide with 200mm long can be fabrication by using the mold casting method.