Integration of chemical vapor deposition aluminum and physical vapor deposition aluminum for aluminum plug process of sub-quarter micron devices

A chemical vapor deposition (CVD)-physical vapor deposition (PVD) Al plug process was successfully integrated to fabricate device wafers with sub-quarter micron technology. Metalorganic CVD (MOCVD) TiN stacked on ion metal plasma (IMP) Ti was used as the underlayer of CVD Al from dimethylaluminum hydride (DMAH). Thin, conformal CVD Al film deposited at a low temperature functioned as an effective wetting layer for PVD Al reflow If the CVD Al film is too thick, a complete via fill is not achieved. After PVD Al reflow, Al bumps were observed atop the via, which originated from the abnormal growth of the Al grain with a non-[111] direction. A two-step PVD Al process was applied for bump removal, because a thin PVD Al layer deposited at low temperature with high power acted as a seed layer far grain growth. The CVD-PVD Al plug process exhibited via resistance and electromigration resistance superior to those of the conventional W plug process.