First Principles Calculation of the Mechanism of Oxygen Precipitation in Czochralski Silicon Crystals : (Effects of Heavy Boron Doping)

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The mechanism of enhancement of the nucleation and growth of oxide precipitates (SiO2) in heavily boron (B)-doped Czochralski (CZ) silicon (Si) crystals was analyzed by first principles calculation. At the initial stage of oxygen precipitation including a small number n of interstitial oxygen (O) atoms with and without one substitutional B atom, i.e., B-On complex and On complex, reduction of the total energy of stable B-On complex formation was greater than that of stable On complex formation from isolated B and O atoms. Other calculations showed that the O atom in B-doped Si diffused as O2+ charge state with a diffusion barrier of about 2.0 eV, which was lower than the barrier of about 2.5 eV for the O0 charge state in intrinsic Si. This reduction of the diffusion barrier should be the mechanism responsible for the enhanced oxygen diffusion and enhanced precipitate growth in heavily B-doped CZ Si crystals.