Minority carrier lifetime in annealed silicon crystals containing oxygen

The influence of oxygen on the minority carrier lifetime of silicon is reported. Bulk annealed, oxygen-rich crystals subsequently sliced into wafers show lifetime degradation with annealing time. Silicon oxide precipitates and punched out dislocation loops induced during annealing are identified as electrically active defects responsible for the observed lifetime degradation. Increase in device yields (diodes) and improved lifetime in epitaxial films obtained with oxygen-rich wafers as substrates are a result of “intrinsic gettering” of oxygen-rich wafers. It is shown that “external gettering” cannot improve minority carrier lifetime in silicon wafers if during processing “intrinsic gettering” is activated. It is also shown that “external gettering” such as impact sound stressing (ISS) is very effective in improving lifetime for wafers not containing “intrinsic gettering” sources.