High-energy ion-implantation-induced gettering of copper in silicon beyond the 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 gettering layers during the subsequent annealing. Then the samples were contaminated with Cu by implanting the impurity on the backface and performing additional annealing. The resulting Cu depth distributions were measured by secondary ion mass spectrometry. Strong gettering of Cu atoms beyond the projected ion range RP and formation of a well-defined separate Cu gettering band therein is found for P and As implants. We call this phenomenon the “trans-RP effect.” It arises from the presence of a significant amount of defects in the regions much deeper than RP. Their gettering ability is higher than that of the extended defects around RP, as the amount of Cu atoms gettered beyond RP is, especially for the P implants, much greater than that in the implanted gettering layer at RP. These deep defects have not been detected by transmission electron microscopy, and we suggest that they are small interstitial clusters. A mechanism responsible for the migration of self-interstitials from RP into the trans-RP region and their clustering therein is proposed. An explanation is given of the possible reasons for the differences in the results for the P+ and As+ implants.