PROXIMITY GETTERING OF TRANSITION-METALS IN SILICON BY ION-IMPLANTATION

We compare the gettering efficiency of C, O and He implantation into Cz-grown silicon. After the getter implantation, with a projected range of 1.2 mu m, we introduce a controlled amount of either Fe or Cu through low-energy implantation. Subsequently, we study the distribution of the impurities for various annealing conditions by means of secondary ion mass spectroscopy. In contrast to the C and O implantations which already show gettering behaviour at relatively low doses, the He implantation requires a dose in excess of 6 X 10(15) ions/cm(2) before observable gettering occurs. When sufficiently high doses of He are implanted its gettering efficiency significantly exceeds that of comparable C and O implantations, i.e. implantations with the same projected ranges and doses, subjected to the same annealing treatment. The shape of the getter profile in the sample implanted with He is strongly influenced by the annealing treatment.