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

Abstract

The strong gettering of Cu atoms in single-crystal Si implanted with 3.5 MeV P+ ions is studied after thermal treatment and Cu contamination. Cu decorates the remaining implantation damage. Three separate Cu gettering layers are 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 determined by binary collision simulations for random and channeled ion incidence. The RP/2 effect for P+ implantation is found to be significantly reduced in comparison with Si+ implantation. It disappears completely for higher P+ ion fluences. 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. These results are in qualitative agreement with the assumption that interstitials carried by P diffusion are the origin of Cu gettering in the trans-RP region. The P diffusion may inject interstitials into the bulk and also into the RP/2 region thus decreasing the RP/2 effect.