Study of reverse annealing behaviors of p+/n ultrashallow junction formed using solid phase epitaxial annealing

Solid phase epitaxial (SPE) annealing at low temperature has the advantage of high dopant activation and very little dopant diffusion. However, due to the low thermal budget engaged in SPE, a large amount of defects can exist in the area beyond the original interface of the crystal and the pre-amorphized layer. These defects may cause severe junction leakage. They may also cause dopant diffusion and deactivation in a following higher temperature process. This work studies the reverse annealing behaviors during a second annealing step for SPE-formed p(+)/n junction using either 1 keV B+ or 5 keV BF2+ implants. Four-point probe, secondary-ion-mass spectroscopy, and transmission electron microscopy are used in this study. The results show that the boron deactivation after second-step annealing is not only correlated with the transmission electron diffraction (TED), but also correlated with the end of range defect evolution. The results also show that BF2 implanted wafer has slower boron deactivation, less TED and slower defect evolution than the B implanted wafer. In addition, the BF2 implanted wafer shows a much slower SPE regrowth rate at 550 degreesC than the B implanted wafer. (C) 2002 American Vacuum Society.