Characteristics of SrTiO₃ thin films deposited on Si by rf magnetron sputtering at various substrate temperatures

Abstract

SrTiO₃ (STO) thin films were deposited on p-type Si(100) substrates by rf magnetron sputtering at various substrate temperatures, and their structural and electrical properties were investigated without post-deposition annealing. The thickness of the films was in the range from 300 to 500 nm while the deposition temperature was varied between room temperature and 550°C. Compositional and structural characterizations included X-ray diffraction, Rutherford back-scattering spectroscopy and variable-angle spectroscopic ellipsometry. Metal-insulator-semiconductor diodes with the configuration of Al/STO/p-Si/Al were fabricated and characterized by capacitance-voltage, current-voltage and admittance spectroscopy measurements. Depending on the substrate temperatures, the dielectric constant of the films varied between 60 and 120 and the loss factor between 0.019 and 0.051 at 100 kHz. All films showed high charge storage capacity, varying between 1.9 and 3μm cm⁻². However, the films deposited at 200°C showed the lowest density of bulk trapped charges (150 nC cm⁻²) and interface states ((1.2–6.1) × 10¹¹ cm⁻² eV⁻¹), and are therefore considered to be the most suitable for device applications.