The effect of Si and Cu on the interactions between Al films and a TiW barrier layer

Abstract

The effect of doping 1 wt % Si or 0.9 wt % Cu to Al films on the interactions between Al and TiW barrier layers at 450 °C was studied. It was found that the first product is always Al12W, which forms at the Al/TiW interface, irrespective of the dopant addition. However, doping 1 wt % Si to Al film enhances the Al12W formation while doping 0.9 wt % Cu retards its formation. With excess tungsten in the system, Al12W would further react with W to form Al/W compounds with higher W content. In pure Al film, both the hexagonal Al5W phase and the monoclinic Al4W phase were detected to form after prolonged annealing at 450 °C. The addition of 1 wt % Si or 0.9 wt % Cu to Al prohibits the formation of Al5W, thus only the Al4W phase was observed at the W/Al12W interface in the doped Al films.