PREPARATION OF TA2AL INTERMETALLIC COMPOUND FILMS AND THEIR APPLICATION AS DIFFUSION-BARRIERS TO CU PENETRATION

The thermal stability of the Cu/Ta2Al/Ta/Si contact system, in which t he intermetallic compound film of Ta2Al is used as a diffusion barrier to copper penetration, has been studied using Auger electron spectros copy analysis. Although the examined contact system degrades by the in terfacial reaction of silicide formation at the Ta/Si interface due to annealing, the system tolerates annealing at 650 degrees C for 1 h if the Ta layer is considered as a consumable barrier, The replacement o f Ta with a Ta-W alloy film results in a decrease of the resistivity a nd an increase of the silicidation temperature due to alloying. By usi ng this alloy film as a layer adjoining to Si, the system of Cu/Ta2Al/ Ta-W/Si tolerates annealing at 680 degrees C for 1 h. Even after this annealing, any penetration of Cu is not observed at the Cu/Ta2Al inter face, suggesting that Ta2Al is a promising material as a diffusion bar rier to copper overlayer films.