Diffusion and Activation of Ultra Shallow Boron Implants in Silicon in Proximity of Voids

Abstract

We have designed a set of experiments in which a controlled supersaturation of vacancies can be maintained constant during annealing of a boron implant. In presence of voids, a remarkable reduction of boron diffusivity is observed and, for low fluence B implantation, TED can be totally suppressed. We show that the presence of nanovoids in the B implanted region is not a prerequisite condition for the reduction of B diffusivity. Large voids located at more than 100 nm apart from the B profile still show the same effect. Small voids can also be used to increase the activation of boron. All these results are consistent with the hypothesis that, during annealing, vacancies are injected from the voids region towards the Is rich region in the implanted region where they massively recombine. Finally, we show that BICs cannot be simply dissolved by injecting vacancies into the region where they stand.