Effect of post-deposition annealing on electrical properties and structures of aluminum oxide passivation film on a crystalline silicon substrate

We studied the effect of post-deposition annealing (PDA) on the electrical property and the structure of aluminum oxide (AlOx) passivation films prepared by atomic layer deposition with various temperatures. Surface recombination velocity (Smax), interface trap density (Dit), and fixed charge density (Qeff/q) before and after the PDA were evaluated employing lifetime and capacitance–voltage measurements. The structural change by the PDA was investigated by a Stokes ellipsometer and X-ray reflectivity (XRR) measurements at SPring-8. The Smax of all samples was improved by the PDA. The improvement of Smax in the samples deposited at the temperature of 200 °C and 300 °C was due to the Dit decrease, but that in the sample deposited at the temperature of 25 °C was due to both the Dit decrease and the Qeff/q increase. From the XRR measurements, it revealed that the formation of the interfacial thin layer is essential for the appearance of negative fixed charges.