Corrosion effects following the etching of Al(Cu 1 %) using a SiCl4/Cl-2/He/CHF3 gas plasma have been evaluated. The phenomenon has been studied using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Auger electron spectroscopy (AES). It was found with SEM that the surface of Al(Cu 1 %) was mainly corroded at the grain boundary. Using AES point analysis, the cause of selective corrosion at the grain boundary of Al(Cu 1 %) has been investigated. The fluorine (F) and chlorine (Cl) on the etched Al(Cu 1 %) have been analyzed with AES. The results showed that the contents of F and Cl on the post-SF6 treated Al(Cu 1 %) were different at each of the analyzed positions such as the grain boundaries and crystalline regions. This seems to result from the imperfect crystalline structure of Al(Cu 1 %) grain boundaries. The effects of subsequent in situ SF6 plasma treatment on the etched Al(Cu 1 %) has been also examined using XPS. It was also confirmed that F has passivated the Cl compounds. The AES and XPS results imply that Cl incorporated at the grain boundaries of the polycrystalline Al(Cu 1 %) film accelerated the corrosion and could not be easily removed by subsequent SF6 plasma treatment.