GETTERING OF IRON TO IMPLANTATION-INDUCED CAVITIES AND OXYGEN PRECIPITATES IN SILICON

Iron gettering at both implantation-induced cavities and oxygen precip itates in silicon was experimentally measured and theoretically modele d. Since impurity removal from the near-surface region is crucial for proper integrated circuit device operation, these experiments strictly tested the viability of each mechanism to sufficiently reduce the nea r-surface Fe concentration. Cavities and oxygen precipitates were form ed by helium implantation in the near surface region and specific heat treatments, respectively. Low doses of intentionally introduced Fe we re gettered with either a short rapid thermal anneal or a long furnace anneal, both at moderate temperatures. The Fe concentration was measu red in the near surface region as well as in the cavities. The cavitie s were found to drastically reduce near-surface Fe concentrations for both anneals while the oxygen precipitates were only fairly effective for long furnace anneals. Furthermore, for samples with both cavities and oxygen precipitates, the gettering of Fe was only slightly enhance d over samples with only cavities. The experimental results were suppo rted by a semiquantitative agreement with modeling based on previously derived theoretical formalisms. These experimental results clearly sh ow an increased gettering effectiveness of implantation-induced caviti es over oxygen precipitates for impurity removal from the near-surface region.