The co-diffusion of B and Sb during post-implantation annealing was investigated in order to fabricate very shallow (70nm) p+/n junctions. The junctions were prepared by first implanting Sb, followed by BF2 (to a higher dose), into an n-type Si substrate. Pre-amorphization with Sb avoided B channelling and increased n-type doping in the junction region; thus limiting the depth of the p layer. Both transient enhanced diffusion, of implanted B in a pre-amorphized layer, and normal diffusion due to pairing between donors and acceptors, were strongly reduced. This permitted very shallow junctions to be obtained even after annealing (800C/8h, 900C/1h, 950C/600s or 1000C/60s). It was demonstrated that dopant diffusion was strongly affected by direct donor-acceptor interaction, and that an accurate prediction of experimental results could be obtained only by using a simulation which took account of the formation of neutral, near-immobile, Sb-B pairs.

Counter-Doped Very Shallow p+/n Junctions Obtained by B and Sb Implantation and Co-Diffusion in Si. S.Solmi: Journal of Applied Physics, 1998, 83[3], 1742-7