As the semiconductor industry moves to 65nm node and beyond, Al metal etch has become more and more challenging for its insufficient amount of photo-resist (PR) to achieve the desired sidewall profile and keep the corrosion free performance simultaneously. In this paper, we focus on the selection of appropriate polymeric gas and identify the effect of various etch polymeric gases on Al metal sidewall profile and their corrosion defect performance. Three typical gases including N2, CHF3 and CH4 are selected in this paper. The observations of scanning electron micrographs indicate N2-based recipe is apt to form the severely tapering sidewall profile while CHF3-based recipe has loose polymer protection over the sidewall, thus leading to much worse corrosion defect performance. As expected, CH4-based recipe outperforms the two above polymeric gases. It not only shows the acceptable sidewall profile but also delivers the defect performance of free corrosion.