Study of silicon–germanium interdiffusion from pure germanium deposited layers

We have studied the Ge–Si interdiffusion from structures in which ∼300 nm-thick pure Ge(:B) layers were grown on Si 200 mm substrates by CVD at 450 °C. As-grown samples were capped with SiO2 and then annealed in the 750–900 °C range for various times. Using the secondary ion mass spectrometry (SIMS) MCs2+ methodology, we measures precisely the Ge diffused profiles. Boltzmann–Matano analysis was used to extract the interdiffusion coefficients. Si–Ge interdiffusion is found to be strongly dependent on the Ge concentration. Also, an effect of dislocations near the Ge/Si original interface is suggested by our results. A physical model including the various observed effects is proposed, that gives a very good agreement with experiments. Finally, we show that the effect of the in situ B doping of the pure Ge layer is to reduce the interdiffusion.