W<i>x</i>N1−<i>x</i> alloys as diffusion barriers between Al and Si

Abstract

Reactively sputtered tungsten nitride (WxN1−x) layers are investigated as diffusion barriers between Al overlayers and Si shallow n+ -p junctions. Both amorphous W80 N20 and polycrystalline W60 N40 films were found to be very effective in preserving the integrity of the n+ -p diodes for 30-min vacuum annealing up to 575 °C. Diode failure at higher temperatures is caused by localized penetration of Al into 〈Si〉 through the WxN1−x barriers. The effectiveness of the barrier decreases for polycrystalline W90 N10 and is worse for pure W.