Boron Profile Sharpening in Ultra-Shallow p{sup +}-n Junction Produced by Plasma Immersion Ion Implantation from BF{sub 3} Plasma

We have investigated plasma immersion ion implantation (PI{sup 3}) of boron with energies of 500 eV (doses up to 2x10{sup 15} cm{sup -2}) from BF{sub 3} plasma with He pre-amorphizing implantation (PAI)(energy 3 keV, dose 5x10{sup 16} cm{sup -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 5x10{sup 19} cm{sup -3}) moves toward the surface and then, as in the usual diffusion, toward the bulk at longer annealing times.