Structure and dielectric properties of BaTi₄O₉ thin films for RF-MIM capacitor applications

BaTi₄O₉ thin films were grown on a Pt/Ti/SiO ₂/Si substrate using RF magnetron sputtering. A homogeneous BaTi ₄O₉ crystalline phase developed in the films deposited at 550°C and annealed above 850°C. When the thickness of the film was reduced, the capacitance density and leakage current density increased. Furthermore, the dielectric constant was observed to decrease with decreasing film thickness. The BaTi₄O₉ film with a thickness of 62 nm exhibited excellent dielectric and electrical properties, with a capacitance density of 4.612 fF/μm² and a dissipation factor of 0.26% at 100 kHz. Similar results were also obtained in the RF frequency range (1-6 GHz). A low leakage current density of 1.0 × 10^-9 A/cm² was achieved at ± 2 V, as well as small voltage and temperature coefficients of capacitance of 40.05 ppm/V² and -92.157 ppm/°C, respectively, at 100 kHz.