Boron-interstitial silicon clusters and their effects on transient enhanced diffusion of boron in silicon

The nature of ion-implantation induced clusters of boron and silicon-self interstitials (BICs), and their effects on transient enhanced diffusion (TED) of B in Si have been investigated in samples predoped with B at different concentrations. Excess Si interstitials have been introduced by Si+Si+ implantation at 60 keV with doses of 1 and 5×1014 cm−2.5×1014 cm−2. The B diffusivity and the amount of B trapped in the clusters have been evaluated from the best fits of simulation-prediction profiles to experimental B profiles, after annealing at 740 and 800 °C for different times. Our results show that the BICs in the beginning act as a sink for interstitials, strongly reducing the TED in the early phases of the annealing. However, being more stable than the Si-interstitial clusters and the {113} defects, they dissolve slowly and can, therefore, sustain a moderate Si-interstitial supersaturation for longer annealing times, even when the Si-interstitial defects are completely dissolved. The data show that the amount of B in the BICs is higher than that of the interstitials; we estimate an average ratio between the B and interstitial concentrations to be about 1.5