Antimony implantation into Si-B doping superlattices—damage and enhanced diffusion

Abstract

The influence of a heavy Sb ion implantation and subsequent annealing cycles in the temperature range of 800–1000 °C on B-delta doping superlattices in silicon layers grown by molecular beam epitaxy (MBE) was analyzed. Secondary ion mass spectroscopy (SIMS) measurements of these structures are used to investigate the generation and diffusion of point defects. The enhanced diffusion of B from the delta doping spikes in as grown and Sb implanted layers was theoretically described by solving the diffusion equation using the point defect model of TSUPREM−4 for different initial point defect distributions. To fit the experimental SIMS profiles the positively charged B-interstitial diffusion coefficient was changed from the default value of D=0.68 cm2/s to D=0.45 cm2/s. It was found that the given MBE growth process produces interstitials and vacancies with an almost constant average value of about 5×1016 cm−3. The Sb-implanted B modulation doped superlattice allows us to obtain a depth profile of the defect concentration. Assuming an overlapping of a constant value of 5×1016 cm−3 for interstitials and vacancies caused by the MBE growth with a distribution coming out of a damage calculation during Sb implantation, consisting of a flat high concentration region with an exponential decrease towards the level of the MBE layer, the main features of the B diffusion profile in the superlattice could be fitted. Thus, a simple initial point defect distribution model after implantation was able to explain the experimental situation.