In Si, implantation of He2+ or H+ ions and subsequent annealing could lead to the formation of nanocavities below the implanted surface of the wafers. These nanocavities, which behaved as trapping sites for metallic impurities, could be located near the devices in integrated circuits in order to induce a proximity gettering. An investigation was made, in float-zone and Czochralski wafers, the trapping of Au by nanocavities formed by implantation of He2+ or H+ ions at 250keV and at a dose of 3 x 1016/cm2 followed by subsequent annealing (750C, 1h). Deep level transient spectroscopy profiles showed that substitutional Au concentration decreases near the cavity band in float-zone and Czochralski samples. The Au profiles obtained by secondary ion mass spectroscopy showed that there was a strong trapping of Au in the cavity band in all samples. In the case of He2+ implanted wafers, this trapping also occurred in the region between the implanted surface and the cavities, and the higher the O concentration, the higher this trapping is. This could be explained by a higher density of implantation induced defects in He2+ implanted samples and by the formation of O-vacancy complexes in this region. In H+ implanted samples, the H passivation of such defects reduced their efficiency as trapping sites. The results suggested that Au trapping was related to Au precipitation which could inject self-interstitials in the bulk and then decreases the substitutional Au concentration near the cavity band even though there was a constant source of Au atoms in these experiments.

Trapping of Gold by Nanocavities Induced by H+ or He2+ Implantation in Float Zone and Czochralski Grown Silicon Wafers. I.Périchaud, E.Yakimov, S.Martinuzzi, C.Dubois: Journal of Applied Physics, 2001, 90[6], 2806-12