Activation of shallow B and BF2 implants in Si using Excimer laser annealing

We have used laser thermal annealing (LTA) to activate shallow B and BF₂ implants in p-type SOI wafers. Several characterization techniques have been employed in our investigations, such as SiPHER photoluminescence (PL) scans, Sheet resistance measurements (R_s), SIMS and AFM analyses. In sub-melt regime, there is no significant redistribution of implanted dopants; furthermore, BF₂ implanted sample exhibits lower boron activation compared with B implanted one. In melt regime, a characteristic box-like doping profile appears, with a depth corresponding to the melting depth controllable by LTA energy setting. However, at a given annealing energy, BF₂-implanted Si has a larger melting depth than the B-implanted one. In both cases, a dramatic enhancement in defect curing (PL Increase) and in dopants activation (Rs decrease) has been observed on melting. On the other hand, surface roughness is suddenly increased with the appearance of peaks in surface morphology around the melting threshold.