Atomistic analysis of the evolution of boron activation during annealing in crystalline and preamorphized silicon

We use kinetic nonlattice Monte Carlo atomistic simulations to investigate the physical mechanisms for boron cluster formation and dissolution in complementary metal-oxide semiconductor (MOS) processing, and the role of Si interstitials in the different processes. For this purpose, B implants in crystalline Si as well as B implants in preamorphized Si are analyzed. For subamorphizing B implants, a high concentration of Si interstitials overlaps with the B profile and this causes a very quick B deactivation for both low- and high-dose B implants. For B implants in preamorphized silicon, B is activated during the regrowth of the amorphous layer if the B concentration is lower than 1020 cm-3 and remains active upon annealing. However, if B concentrations higher than 1020 cm-3 are present, as occurs in the formation of extensions in p -channel MOS transistors, B atoms are not completely activated during the regrowth. Moreover, the injection of Si interstitials from the end-of-range defects leads to additional B deactivation in the regrown layer during subsequent annealing. If the end-of-range defects overlap with a B profile, even of relatively low concentration, as it occurs for B pockets in n -channel MOS transistors, very quick and local B deactivation occurs in the high Si-interstitial concentration region.