Impurities in Silicon Crystals and Silicon Epitaxial Films: Recent Advances

A high quality of epitaxial silicon layers grown on Czochralski single crystal substrates is required in semiconductor technology, since it directly influences device parameters and yield. Unintentional doping of these layers from the substrate is well documented in the literature. However, we found no reports on unintentional contamination of epi-layers due to the oxygen present in the substrate. The use of micro Fourier transform infrared spectroscopy in transversal mode is shown to be a powerful technique for oxygen profiling and precipitation studies at the same time. It is found that oxygen behaviour during epitaxial layer growth, even for lightly B and P doped substrates, is significantly different. Oxygen, that in some cases diffuses into the grown epitaxial layer, tends to form precipitates there. This is an important consequence of outdiffusion since it directly influences the quality of the epitaxial layer.