CMP (chemical mechanical polishing) and the post-CMP cleaning for damascene processes are necessary to produce Cu interconnects. Many kinds of additives, such as an oxidizer, an inhibitor, etching chemicals, are usually in the CMP slurries. Cu films, however, are easily oxidized and corroded by those chemicals, so it is important to choose the chemicals and to decide how long Cu films are treated with them. If we can grasp the residues on Cu films and the Cu oxidation, it will be easy to optimize the conditions of CMP processes. Then we treated Cu films with benzotriazole (BTA), a well-known Cu corrosion inhibitor, in some conditions, and we investigated the residues and the Cu oxidation. The results of TOF-SIMS measurements seem to correlate with the results of XPS measurements. Ions derived from BTA are at high relative intensities in a sample treated with high concentrated BTA, and it is not so highly oxidized. On the other hand, they are at low relative intensities in a sample treated with acids, and it is rapidly oxidized. These analysis methods can be applied in various fields. (C) 2002 Elsevier Science B.V. All rights reserved.