Boron Profile Sharpening in Ultra-Shallow p+-n Junction Produced by Plasma Immersion Ion Implantation from BF3 Plasma

We have investigated plasma immersion ion implantation (PI3) of boron with energies of 500 eV (doses up to 2X1015 cm-2) from BF3 plasma with He pre-amorphizing implantation (PAI) (energy 3 keV, dose 5X1016 cm-2). Implanted samples were subjected to RTA (T = 900 to 1050 deg C, t = 2 to 24 sec and spike anneal). SIMS analysis of boron profiles revealed its anomalous behavior. For short RTA times the profile tail (below 5X1019 cm-3) moves toward the surface and then, as in the usual diffusion, toward the bulk at longer annealing times.