Microstructure and dielectric properties of the Ti-rich BaO–TiO2 thin films for microwave devices

Ti-rich BaO–TiO2 thin films were grown on a Pt/Ti/SiO2/Si substrate using rf sputtering and the structural and dielectric properties of the films were investigated. For the film grown at room temperature and rapidly thermal annealed (RTA) at 900 °C for 3 min, an amorphous phase with a small BaTi5O13 crystalline phase was formed. As the growth temperature increased, the amount of the BaTi5O11 crystalline phase increased. For the film grown at 350 °C and RTA at 900 °C for 3 min, the homogeneous BaTi5O11 phase was formed. The BaTi4O9 phase was developed when the growth temperature exceeded 450 °C. The thin film with the homogeneous BaTi4O9 phase was obtained when the film was grown at 550 °C and RTA at 900 °C for 3 min. The dielectric properties of the films were measured at 1–6 GHz range. The dielectric constant (ϵr) of the BaTi5O11 film was about 33 and the dissipation factor was about 0.01. The ϵr and the dissipation factor of the BaTi4O9 film were about 37 and 0.005, respectively.