During post-chemical mechanical polishing (CMP) cleaning of copper Damascene structures by diluted hydrofluoric acid (HF), a corrosion phenomenon has been shown on patterned wafers, leaving a copper deposit and an associated copper etching. Methods are developed to eliminate the phenomenon hy use of benzotriazole or crotonic acid in the diluted HF solutions. At the same time, the presence of these inhibitors does not change the cleaning efficiency of the diluted HF solutions. Also, the elimination of light during the cleaning step eliminates the corrosion. A theoretical explanation is given.