The evolution of surface chemical species on etched Al (Cu) lines and films has been investigated by X-ray photoelectron spectroscopy in a postetch cleaning process, with the aim of understanding the role of each step on the removal of the etching residues. The results from the in situ strip in downstream H2O plasma show that most of the organic species are removed by oxidation reactions, together with the majority of the Cl species. However, the sidewall polymer leaves a Cl-containing residual film due to its high metallic content and oxidation reactions. Adding a small amount of CF4 to the H2O plasma can have some advantages mainly making the residues more water soluble. Further ex sial wet chemical treatment is needed to remove the oxide/fluoride layer formed in the in situ step. Tt is argued that a clean surface, consisting of Al bonded strongly to its native oxide, is essential to the reliability of the interconnect. It is also found that after dry etching there are two kinds of Cu species present at the Al surface layers. One is a CuClx residue, which can be removed effectively by the cleaning. The other is elemental Cu enrichment. Rutherford backscattering spectrometry results reveal that this enrichment distributes over a depth of about 40 nm in Al, with a peak concentration of two to three times the bulk value.