We prepared alumina passivation films deposited by a sol-gel wet process for silicon substrates. Aluminum acetylacetonate was used as a precursor, and the solution was spin-coated onto silicon substrates. Calcination temperature dependence of the passivation quality of the films was evaluated mainly by measuring effective lifetime using a photo conductance decay technique and capacitance-voltage measurements. Also, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were carried out to evaluate film properties. A large amount of negative fixed charge density (Q(f) = -3.1 x 10(12) cm(-2)) exists in the films calcined at 300 degrees C. On the other hand, a long effective lifetime of 400 mu s was obtained for the sample calcined at 600 degrees C, and the passivation films had a large amount of positive fixed charge density (Q(f) = 3.6 x 10(12) cm(-2)) with a low interface state density. (C) 2015 Elsevier B.V. All rights reserved.