Narrowing or broadening of the B profile during annealing of laser-processed samples was observed to occur depending upon which of 2 competing mechanisms, up-hill B diffusion, due to a highly defective single-crystal layer near the surface, or transient-enhanced diffusion due to end-of-range defects, predominated during post-laser processing annealing. The results showed that up-hill B diffusion predominated, during the annealing of a single-pulse laser-processed sample, because defects near to the surface could not be efficiently removed by a single laser pulse of a magnitude that could melt the amorphous material but not the underlying crystal. With successive laser pulses, the dopants moved deeper into the Si during subsequent rapid thermal annealing cycles. This was attributed to a reduced contribution of up-hill B diffusion when defects near to the surface decreased with successive pulses. End-of-range defects, which could not be sufficiently annealed out because the melt depth did not extend beyond the amorphous layer, therefore played a key role in broadening the B concentration profile in multiple-pulse laser-annealed material.

Boron Profile Narrowing in Laser-Processed Silicon after Rapid Thermal Anneal. C.H.Poon, L.S.Tan, B.J.Cho, A.See, M.Bhat: Journal of the Electrochemical Society, 2004, 151[1], G80-3