The interactions of copper and copper oxide layers with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (H(+)hfac) have been investigated. The results provide supporting evidence for proposed reactions of copper with H(+)hfac which are thought to be responsible for the vapor-phase etching of copper. Specific reaction products depend on the chemical state of the copper in the film. Reaction of H(+)hfac with Cu2+ yields volatile reaction products of Cu-II(hfac)(2) and H2O, while Cu1+ yields the same products with a change in the chemical state of the surface to Cu-(0). No reaction is observable between H(+)hfac and Cu-(0) at temperatures studied in these experiments.