Al-Si crystallographic-orientation transition in Al-Si/TiN layered structures and electromigration performance as interconnects

Abstract

Formation of aluminum-silicon (Al-Si) alloy/titanium nitride (TiN) layered structures and their electromigration (EM) performance have been investigated. The crystallographic structure of the TiN film changes with the sputter-deposition conditions. A large negative substrate bias in reactive sputtering induces a structural transition in the TiN film. The crystal orientation normal to the film surface is easily controlled from the 〈111〉 to the 〈200〉 direction. The crystallographic orientation of the Al-Si alloy film has been successfully controlled by the film deposition on an orientation controlled barrier TiN film. The Al-Si alloy film grows epitaxially on TiN at the initial stage of deposition and this causes the Al-Si alloy’s preferred orientation to the underlying TiN film. These layered structures with different levels of Al-Si alloy preferred orientation have been subjected to EM tests, and the Al-Si alloy film with stronger 〈111〉 orientation was found to have a longer EM lifetime. The best EM resistance has been obtained on Al-Si alloy film with the strongest 〈111〉 orientation, which is achieved on a TiN film formed by the nitridation of a titanium (Ti) film. Thus, highly reliable interconnects can be obtained by improving the preferred orientation of Al-Si alloy film using texture improved TiN film.