Spatial distribution of cavities in silicon formed by ion implantation generated excess vacancies

The spatial distribution of nanosized cavities in silicon formed by high energy Ge ion implantation and annealing is determined. The cavities are directly observed by transmission electron microscopy without any metal decoration. They are shown to be the agglomerates of implantation-induced excess vacancies. The concentration depth profile of the vacancies bound in the cavities agrees well with the excess vacancy profile calculated for the implantation process. Almost all the generated excess vacancies agglomerate in cavities after annealing at 900 °C for 30 s. The vacancy profile shape coincides with the depth profile of Cu that was intentionally introduced in the cavity region. The perfect match of vacancy and Cu distribution indicates the cavities are the determining gettering centres for Cu atoms in ion implanted Si.