Ti and V layers retard interaction between Al films and polycrystalline Si

Abstract

Fine-grained polycrystalline Si (poly Si) in contact with Al films recrystallizes at temperatures well below the Si-Al eutectic (577 °C). We show that this interaction can be deferred or suppressed by placing a buffer layer of Ti or V between the Al film and the poly Si. During annealing, Ti or V form TiAl3 or Val3 at the buffer-layer–Al-film interface, but do not react with the poly Si so that the integrity of the poly Si is preserved as long as some unreacted Ti or V remains. The reaction between the Ti or V layer and the Al film is transport limited (∝t1/2) and characterized by the diffusion constants 1.5×1015 exp(−1.8eV/kT) Å2/sec or 8.4×1012 exp(−1.7eV/kT) Å2/sec, respectively.