EFFECT OF NITROGEN CONTAMINATION BY CRUCIBLE ENCAPSULATION ON POLYCRYSTALLINE SILICON MATERIAL QUALITY

This paper reports some results about a recently discovered sourer of lifetime degradation found in polycrystalline silicon ingots grown in silicon-nitride-lined silica crucibles. A systematic analysis of the l ow lifetime areas, which preferentially are found corresponding to the ingot edges and corners, carried out using different structural, spec troscopical and electrical techniques, shows that the lifetime drop is associated with the presence of a high density of silicon nitride and iron silicide submicrometre particles, revealed by transmission elect ron microscopy and electron diffraction measurements. An at least part ial recovery of the lifetime is obtained by P gettering at 900 degrees C, which seems to be effective in dissolving the iron silicide from t he nitride-rich areas.