WxN1−x alloys as diffusion barriers between Al and Si

Abstract

Reactively sputtered tungsten nitride (W_xN_1−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 W_xN_1−x barriers. The effectiveness of the barrier decreases for polycrystalline W₉₀ N₁₀ and is worse for pure W.