SIMS INVESTIGATIONS OF GETTERING CENTERS IN ION-IMPLANTED AND ANNEALED SILICON

ABSTRACT High-energy ion implantation in silicon leads to the formation of defects around the mean projected ion range R p. These defects are capable of collecting unwanted impurities like metal atoms. A similar effect has been observed in the depth range around half of the projected ion range, R p/2. This gettering ability around R p/2 is supposed to rely on excess vacancies, generated by the implantation process itself. SIMS is a preferential tool in the detection of gettering centres: If copper is applied at the backside of the sample and trapped in the gettering layers during annealing, enrichments of copper in certain areas can be seen in SIMS depth profiles [1]. If the R p/2-effect was caused by excess vacancies, then one attempt to remove these additional gettering centres would be to implant additional Si atoms which could recombine with the vacancies: In order to test this assumption, three Si+ implanted samples were implanted with additional Si+ ions having a projected range that corresponds to R p/2. After application of copper and annealing, the copper distribution was investigated by SIMS. Furthermore a low-energy-He+-implanted silicon wafer was examined, showing that He+ implantation not only leads to an accumulation of metals but also of oxygen in the R p and R p/2 range.