Preparation of Ta2Al intermetallic compound films and their application as diffusion barriers to Cu penetration

Abstract

The thermal stability of the CuTa2AlTaSi contact system, in which the intermetallic compound film of Ta2Al is used as a diffusion barrier to copper penetration, has been studied using Auger electron spectroscopy analysis. Although the examined contact system degrades by the interfacial reaction of silicide formation at the TaSi interface due to annealing, the system tolerates annealing at 650 °C for 1 h if the Ta layer is considered as a consumable barrier. The replacement of Ta with a Ta-W alloy film results in a decrease of the resistivity and an increase of the silicidation temperature due to alloying. By using this alloy film as a layer adjoining to Si, the system of CuTa2AlTa-WSi tolerates annealing at 680 °C for 1 h. Even after this annealing, any penetration of Cu is not observed at the CuTa2Al interface, suggesting that Ta2Al is a promising material as a diffusion barrier to copper overlayer films.