Lateral incorporation of vacancies in Czochralski silicon crystals

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Silicon crystals grown by the Czochralski process typically contain many structural imperfections termed microdefects. The formation of microdefects requires an abundance of one of the intrinsic point defect species of silicon, vacancies or self-interstitials. The distribution of microdefects in a growing Czochralski crystal is influenced by its temperature field and the boundary conditions defined by its surfaces. This paper addresses the effects of the lateral surface on the defect dynamics in a growing crystal in which both the intrinsic point defect species are in comparable and low concentrations, away from the lateral surface, at higher temperatures near the melt/crystal interface. Under such conditions, a moderate vacancy supersaturation develops in the vicinity of the lateral surface leading to the formation of oxygen clusters and small voids, at lower temperatures. The vacancy incorporation near the lateral surface is driven by an interplay among the Frenkel reaction, the diffusion of the intrinsic point defects, and their convection.