Deposition of copper on ruthenium for Cu metallization

Abstract

The morphology and behavior of thin Cu films deposited using electroless, electrolytic, and physical vapor deposition (PVD) is studied using Ru as a substrate. Ru was deposited by both PVD and atomic layer deposition (ALD). Electrolessly deposited Cu on PVD Ru resists agglomeration with annealing, while on ALD Ru it exhibits a tendency for agglomeration when annealed. Electrolytically deposited Cu on PVD Ru also resists agglomeration if the Ru to Cu plating queue time is short; on ALD Ru, it appears agglomerated as-deposited, even for short Ru to Cu plate queue times. In contrast to electrochemically deposited Cu, PVD Cu does not agglomerate with anneal on either PVD or ALD Ru, even for long Ru-Cu queue times. Auger spectroscopy suggests that ALD Ru has more oxygen and nitrogen at the surface as compared to PVD Ru. The possible roles of these impurities in impacting the deposited Cu morphology are briefly discussed. ©The Electrochemical Society.