Computing Diffusion Coefficients of Intrinsic Point Defects in Crystalline Silicon

The quality of crystalline silicon highly influences the quality of semiconductor devices fabricated with it. Grown-in defects, such as octahedral voids or networks of large dislocation loops can be detrimental to the functionality of devices. Both type of defects result from the interaction of intrinsic point defects, vacancies and self-interstitials during growth and subsequent annealing of the crystal. In order to qualitatively describe the formation of microdefects in crystalline silicon, a detailed understanding of intrinsic point defects is necessary. Modeling of defect dynamics in silicon crystals during growth requires the description of physical phenomena on different length and time scales. Continuum balance equations are used to describe the distribution, transport and kinetic interactions of point defects, either vacancies or selfinterstitials, throughout the crystal as a function of the local temperature.9 These equations contain highly temperaturedependent material properties, which describe atomistic events, such as the diffusion of a self-interstitial through the silicon lattice or the recombination of a vacancy with a selfinterstitial. The absence of direct experimental measurements of intrinsic point defect properties at high temperatures make it necessary to compute these properties from atomistic simulations based on empirical or semiempirical atomistic models. Here, the microscopic quality of the crystal is given by the intrinsic point defect concentration. In order to understand the dynamics of these defects large scale molecular dynamics simulations based on the potentials of Stillinger-Weber and Tersoff are performed and the temperature dependence of the diffusion coefficients for selfinterstitials and vacancies is computed.