Precipitation of iron in FZ and Cz silicon

Iron was precipitated in FZ silicon and Ct silicon with varying densities of oxygen precipitates, including Ct material with no oxygen precipitates. Computer simulations based on Ham's law were fitted to experimental data to obtain iron precipitation site densities. Iron precipitate densities were found to decrease with increasing precipitation anneal temperatures until approximate to 500 degrees C, yielding a trap energy of 0.49+/-0.14 eV. Above 500 degrees C, the precipitation site density remained approximately constant. Iron precipitate site densities increased with oxygen precipitate densities, and correlated with oxygen precipitate surface areas. Iron precipitate site densities in FZ material were found to be higher than in Ct with no oxygen precipitates. We suggest that vacancy agglomerations may be the dominant trapping defect in FZ.