Al-Ge reflow sputtering for submicron-contact-hole filling

Aluminum-germanium (Al-Ge) reflow sputtering was developed for submicron contact hole and via filling. The Al-Ge step coverage and effects of underlayers (poly-Si, MoSi₂, TiW) on the Al-Ge filling characteristics were investigated. It was found that the Al-Ge flowed and the grains grew to approximately 5 μm diameter during sputtering in the temperature range between 200°C and 300°C. It was also found that Si atoms played an important role for submicron contact hole and via fillings in helping the Al-Ge into the bottoms of holes and vias. The contact holes with a diameter of 0.25 μm and aspect ratio of 4 were successfully filled with the Al-Ge by using a poly-Si underlayer deposited before the sputtering. The contact resistances of holes filled with the Al-Ge as well as the electromigration life time of the Al-Ge were comparable to those of conventional Al