Effect of a mid-temperature thermal annealing on the enhancement of boron diffusion during rapid thermal annealing

Abstract

Silicon samples containing a sequence of boron spikes grown by molecular beam epitaxy have been used in this work. Point defects were introduced near the surface by means of room temperature silicon implantation. The ion profile was confined between the surface and the first boron spike. The presence of self-interstitials enhances the boron diffusion in ion-implanted and subsequently annealed samples. Two kinds of thermal annealing were used for this study on implanted samples: a mid-temperature annealing (700°C, 20min) and a rapid thermal annealing (950°C, 20s). The aim of the present study was to investigate if a mid-temperature annealing could significantly reduce boron diffusion during a subsequent rapid thermal annealing. It is shown in this work that the slight reduction in interstitial excess concentration during the mid-temperature annealing is not sufficient to substantially influence the boron diffusion during a subsequent rapid thermal annealing. It appears, therefore, that this original idea, already presented in another work, is of limited interest from a technological point of view.