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 BaTi₅ O₁₃ 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 (ε_r) of the BaTi₅ O₁₁ film was about 33 and the dissipation factor was about 0.01. The ε_r and the dissipation factor of the BaTi₄O₉ film were about 37 and 0.005, respectively.