Formation and nature of swirl defects in silicon |
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Authors: | H Föll B O Kolbesen |
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Institution: | 1. Institut für Physik, Max-Planck-Institut für Metallforschung, D-7000, Stuttgart 80, Germany 2. Siemens AG, Grundlagenentwicklung Halbleiter, P.O. Box 460705, D-8000, München 46, Germany
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Abstract: | Point defect agglomerates in dislocation-free silicon crystals, usually called “swirls”, have been investigated by means of high-voltage electron microscopy. It was found that a single swirl defect consists of a dislocation loop or a cluster of dislocation loops. By contrast experiments it could be shown that these loops are formed by agglomeration of self-interstitial atoms. Generally the loops have a/2〈110〉 Burgers vectors, but in specimens with high concentrations of carbon (~1017 cm?3) and oxygen (~1016 cm?3) also dislocation loops including a stacking fault were observed. In crystals grown at growth rates higher thanv=4 mm/min no swirls are observed; lower growth rates do not markedly affect the size and shape of the dislocation loops. With decreasing impurity content (particulary of oxygen and carbon) the swirl density decreases, whereas the dislocation loop clusters become larger and more complex. A model is presented which describes the formation of swirls in terms of agglomeration of silicon self-interstitials and impurity atoms. |
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