Ionized-PVD stacked barrier structure of TaN/TaRu for 32nm BEOL integration

Abstract

An ionized-PVD stacked barrier structure of TaN/TaRu was developed for 32nm BEOL integration. The TaN layer serves as a most robust diffusion barrier layer, while the TaRu barrier layer improves wettability of the ionized-PVD Cu seed layer. Observed benefits included enhanced Cu gap filling performance, resolving a line voiding problem, improvement in electromigration performance, and higher via chain yield than TaN/Ta controls at 32nm BEOL dimension. This stacked barrier structure, which uses two PVD chambers incorporating pure Ta and TaRu targets, was proposed based on our material studies showing that neither TaRu nor TaRuN performed adequately alone as Cu and O2/H2O diffusion barriers, but performed well when in conjunction with TaN or TaN/Ta backing layers. The newly proposed TaN/TaRu stacked barrier is a possible solution to extend ionized PVD to 32 nm node BEOL. © 2009 Materials Research Society.