High-energy ion-implantation-induced gettering of copper in silicon beyondthe projected ion range: The trans-projected-range effect

Five different species, namely B, Si, P, Ge, and As, were implanted at MeV energies into (100)-oriented n-type Czohralski Si, in order to form deep ge ttering layers during the subsequent annealing. Then the samples were conta minated with Cu by implanting the impurity on the backface and performing a dditional annealing. The resulting Cu depth distributions were measured by secondary ion mass spectrometry. Strong gettering of Cu atoms beyond the pr ojected ion range R-P and formation of a well-defined separate Cu gettering band therein is found for P and As implants. We call this phenomenon the " trans-R-P effect." It arises from the presence of a significant amount of d efects in the regions much deeper than R-P. Their gettering ability is high er than that of the extended defects around R-P, as the amount of Cu atoms gettered beyond R-P is, especially for the P implants, much greater than th at in the implanted gettering layer at R-P. These deep defects have not bee n detected by transmission electron microscopy, and we suggest that they ar e small interstitial clusters. A mechanism responsible for the migration of self-interstitials from R-P into the trans-R-P region and their clustering therein is proposed. An explanation is given of the possible reasons for t he differences in the results for the P+ and As+ implants. (C) 2000 America n Institute of Physics. [S0021-8979(00)05922-3].