Effects of Oxidation on Aluminum Diffusion in Silicon

Aluminum diffusion in Si affected by thermal oxidation is investigated. Aluminum diffusion in (100) oriented Si is enhanced by thermal oxidation. On the other hand, that in (111) oriented Si is enhanced at low temperature but retarded at high temperature. The difference in the diffusion of Al in Si masked with double-layered SiO 2 –Si 3 N 4 films and with directly-formed Si 3 N 4 films is found to be very small compared to the case of B and P. Furthermore, the addition of HCl to the oxidizing ambient is found to reduce the anomalous diffusion caused by oxidation. These experimental results are explained assuming that the diffusion of Al in Si proceeds by the interstitialcy mechanism in the Si.