Chemical mechanical planarization of barrier layers by using a weakly alkaline slurry

Abstract

A weakly alkaline barrier slurry (pH = 8.0) was proposed, which was free of unstable H2O2 and inhibitor such as benzotriazole (BTA). The polishing results of Cu, Ta and oxide blanket wafers show that the slurry has a high removal rate on oxide, while Ta has a low removal rate on Cu. The evaluation of the slurry was implemented in a way that the process conditions of Cu CMP and consumables on platen 1 and platen 2 were fixed. Copper dishing and oxide erosion have been characterized as a function of polishing time. The experiment results reveal that the barrier slurry without inhibitors has an obvious effect on the correction of dishing and erosion, and it also suggests that the slurry has a high selectivity of Ta and oxide to Cu. The sheet resistance does not exhibit any difference as polishing time increased, which indicates substantially lower copper loss.