The diffusion of C into Si was known to be well-behaved and did not generate any non-equilibrium point defects. On the other hand, the diffusion of C at concentrations that were well above its solid solubility produced an undersaturation of Si self-interstitials. These, in turn, could lead to retarded B diffusion.

Carbon-Induced Undersaturation of Silicon Self-Interstitials. R.Scholz, U.Gösele, J.Y.Huh, T.Y.Tan: Applied Physics Letters, 1998, 72[2], 200-2