Cu gettering in ion implanted and annealed silicon in regions before and beyond the main projected ion range

The strong gettering of Cu atoms in single-crystal Si implanted with 3.5 MeV P+ ions was studied after thermal treatment and contamination with low amount of Cu impurity. Cu decorates the remaining damage generated by ion implantation. Three separate Cu gettering layers were detected by secondary ion mass spectrometry: at the main projected ion range, RP, below RP (RP/2 effect) and beyond RP (trans-RP effect). The defects acting as gettering centers at RP/2 and RP are implantation induced excess vacancies and excess interstitials, respectively. Cu profiles fit very well with depth distributions of excess vacancies and excess interstitials simulated by binary collision model for random and channeled ion incidence. The RP/2 and RP gettering layer are implantation induced, whereas the trans-RP gettering layer is formed by thermal treatment. The Cu accumulation in the trans-RP region increases with increasing temperature and/or with increasing annealing time. The RP/2 effect for P+ implantation was found to be significantly reduced in comparison with Si+ implantation. It completely disappears for higher P+ ion fluences. The obtained results are in agreement with the assumption that interstitials carried by P diffusion are the origin of Cu gettering in the trans-RP region.