Plasma cleaning technology in the dual damascene process
In the dual damascene process, it is very difficult to strip plasma-induced hardened photo resist (PR) and bottom anti-reflective coating (BARC) materials using O2 plasma. The residues can be removed effectively using an Ar/O2 mixed plasma due to Ar ion enhancements. However, bowing via of the dual damascene structure is found, resulting in the loss of the via chain yield. For the via first approach, the facets occur at the line/via intersections after trench etching. It is believed that ions reflect from facets at the line/via intersection to via sidewalls during Ar/O2 plasma cleaning, subsequently resulting in bowing via profiles. Experiments also indicate that yield loss depends on different test structures. According to the mechanism of resulting in bowing via profiles, improved via chain yields will be achieved when Ar/O2 plasma (first step) and then O2 plasma (second step) are used.
plasma cleaning dual damascene via chain yield bowing via profile