The oxidation and reduction characteristics of sputter-deposited Cu thin film with a < 111 > preferred orientation have been studied. It was found that Cu oxide, which is identified as Cu2O phase, is easily formed by annealing at 200 degrees C in an O-2 ambient. The linear relation between Cu2O thickness and the square root of oxidation time indicates that the oxidation process of Cu films obeys a parabolic rate law at temperatures from 200 to 280 degrees C. The activation energy of the oxidation reaction in the Cu film was 0.89 eV. The oxidized Cu films were reduced by H-2 annealing at 300 degrees C. The Cu2O formed in the Cu metal of a partially oxidized film was reduced at about 5 min, and the sheet resistance decreased to that of an as-deposited Cu film. The sheet resistance of a fully oxidized Cu film decreased with annealing time and saturated after about 10 min. As a result, the preoxidation sheet resistance could not be recovered. This incomplete recovery is due to the formation of voids in the reduced Cu film. Void-free reduced Cu films with low sheet resistance can be obtained by using appropriate temperatures and pressures during the H-2 annealing. (c) 2005 The Electrochemical Society. All rights reserved.