We use kinetic nonlattice Monte Carlo atomistic simulations to investigate the physical mechanisms for boron cluster formation and dissolution in complementary metal-oxide semiconductor ͑MOS͒ 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 10 20 cm −3 and remains active upon annealing. However, if B concentrations higher than 10 20 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.

We have investigated the atomistic mechanism behind the irradiation-induced amorphization in Si using molecular dynamics simulation techniques. The microscopic description of the process is based on the defect known as bond defect or IV pair. IV pairs recombine very fast when isolated, but if they interact to each other they survive longer times and thus accumulate giving rise to amorphization. This fact accounts for the superlinear behavior of the accumulated damage with dose and the different activation energies for recrystallization observed in the experiments. The molecular dynamics results have been used to define an atomistic model for amorphization and recrystallization which has been implemented in a kinetic Monte Carlo code. The model is able to reproduce quantitatively the dependence of the critical crystal-amorphous transition on the irradiation parameters.

We use kinetic nonlattice Monte Carlo atomistic simulations to investigate the physical mechanisms for boron cluster formation and dissolution at very high B concentrations, and the role of Si interstitials in these processes. For this purpose, high-dose, low-energy B implants and theoretical structures with fully active box shaped B profiles were analyzed. Along with the theoretical B profile, different Si interstitial profiles were included. These structures could be simplifications of the situation resulting from the regrowth of preamorphized or laser annealed B implants. While for B concentrations lower than 1020 cm−3, B clusters are not formed unless a high Si interstitial concentration overlaps the B profile, our simulation results show that for higher B concentrations, B clusters can be formed even in the presence of only the equilibrium Si interstitial concentration. The existence of a residual concentration of Si interstitials along with the B boxes makes the deactivation faster and more severe.

We propose an atomistic model to describe the evolution of the damage generated by irradiation in Si, going from isolated point defects to the formation of continuous amorphous layers. The elementary units used to reproduce the defective zones are Si interstitials, vacancies and the bond defect, which is a local distortion of the Si lattice without any excess or deficit of atoms. More complex defect structures can be formed as these elementary units cluster. The amorphous pockets are treated as agglomerates of bond defects characterized by their local coordination. The model is able to reproduce the abrupt regime in the crystal-amorphous transition in Si and the epitaxial recrystallization upon annealing as observed in the experiments. The model extends the atomistic kinetic Monte Carlo simulation technique to high implant doses, adequately describing the amorphization and regrowth in Si.

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