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

Abstract

We studied the effect of post-deposition annealing (PDA) on the electrical property and the structure of aluminum oxide (AlO x ) passivation films prepared by atomic layer deposition with various temperatures. Surface recombination velocity (S max), interface trap density (D it), and fixed charge density (Q eff/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 S max of all samples was improved by the PDA. The improvement of S max in the samples deposited at the temperature of 200 °C and 300 °C was due to the D it decrease, but that in the sample deposited at the temperature of 25 °C was due to both the D it decrease and the Q eff/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.