The chemical and mechanical properties of wafer materials have a direct impact on the performance of the CMP process. This report presents a systematic study to characterize surface films on copper wafers in the presence of simple peroxide solutions as well as representative bulk copper and copper barrier CMP slurries offered by the Dow Chemical Company. Measurements are made of chemical composition, thickness, modulus, and removal rate of films formed under both static etch and CMP conditions. Sample aging-a major obstacle in past efforts of this type-is minimized by temporarily setting up the equipment for wafer film preparation in close proximity to the surface analytical instruments. It is found that Dow's commercial bulk and barrier Cu CMP slurries form permeable surface films less than 4 nm deep consisting of reaction products with copper. Compared to native copper, the films have compressive and shear moduli that are 5X and 2X lower respectively-enabling mechanical removal by sliding contact with pad asperities at a lower threshold contact pressure. The results provide insight into the mechanism of surface film formation during CMP and lay groundwork for modeling the mechanical and chemical steps in the wafer planarization process.