Structure Defects in Pyrolytic Silicon Epitaxial Films

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Abstract
Metallographic and electron microscopic examination of defects in silicon epitaxial films, grown on silicon wafers on graphite heaters, disclose the origin and characteristics of ``faults'' and tetrahedral growths. The occurrence of ``snowstorm'' spheres has also been investigated. Silicon carbide has been identified epitaxial on (111) substrates etched in hydrogen. The carbide grows as thin needles against the {1̄1̄2} step risers of the [111] zone. The steps appear to be formed during the room temperature oxidation of the silicon wafer surface prior to hydrogen etch. The ``faults'' are shown to be twin lamellae resulting from overgrowth of the carbide by the silicon. The methane transport reaction is proposed as the cause of carbide formation. Tetrahedral growths are shown to result from silicon nucleating directly on the carbide away from surface steps. They are twinned to the substrate, and grow faster than the adjacent epitaxial film. Their growth morphology is discussed. The spheres are polycrystalline silicon—silicon carbide matrices apparently resulting from reacted carbon particles which settle upon the substrate at the same time.

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