Boride-enhanced diffusion in silicon: Bulk and surface layers

Epitaxial silicon boride layers, located at the surface or within the bulk of single-crystal silicon, give rise to enhanced diffusion of B during annealing. A submonolayer buried boride layer releases ≈0.4 interstitials per B atom in the layer, generating a transient diffusion enhancement in the range of 10–100 for several minutes at 900 °C. The resulting profile broadening is comparable to that caused by ion implantation damage. At the same temperature, surface boride layers generate a diffusion enhancement of ∼6, part of which arises from the B diffusion flux and part from the chemical influence of the boride layer.