Alumina film deposited by spin-coating method for silicon wafer surface passivation

In the present work, alumina gel was developed for passivating silicon wafers. The alumina gel was prepared by sol–gel method with aluminum sec-butoxide as precursor. After coating, rapid thermal process (RTP) was conducted to activate the passivation effect. X-ray photoelectron spectroscopy and C–V curve were executed to evaluate film properties. The peak at 74.35 eV confirmed the formation of Al₂O₃. Meanwhile, a small peak at low binding energy decreased with the growth of annealing temperature, which was ascribed to the escape of hydrogen, leading to the decline of effective lifetime after 700 °C. The highest fixed charge (Q_f) of − 1.16e12 cm⁻² and superior interface defect density at mid gap (D_it) of 1.98e12 cm⁻²eV⁻¹ were obtained at the annealing temperature of 700 °C, contributing to the highest effective minority carrier lifetime of 292 µs. The present work will be helpful to provide a more cost-effective technique for Al₂O₃ passivation.