Methods for cleaning semiconductor wafers following chemical mechanical polishing are provided. An exemplary method exposes a wafer to a thermal treatment in an oxidizing environment followed by a thermal treatment in a reducing environment. The thermal treatment in the oxidizing environment both removes residues and oxidizes exposed copper surfaces to form a cupric oxide layer. The thermal treatment in the reducing environment then reduces the cupric oxide to elemental copper. This leaves the exposed copper clean and in condition for further processing, such as electroless plating.