Lateral gettering of iron and platinum by cavities induced by helium implantation in silicon

The aim of this study is to characterize the lateral gettering of iron and platinum atoms by introducing cavities at the periphery of large active device areas. Cavities have been obtained by helium implantation (5x1016 He+/cm2, 40 keV) followed by a thermal treatment on samples previously contaminated by iron and platinum. These cavities are known to be efficient in trapping metallic impurities in silicon by chemisorption. The wafers were annealed in the range of 800-1000 deg. C for several minutes in a neutral ambience (N2). The metallic distribution has been monitored in each active device area by using current versus voltage and deep level transient spectroscopy techniques (DLTS). A symmetrical distribution of metallic impurities and current values has been observed in each active region. The influence of cavities extends laterally to several millimeters depending on the temperature and time of diffusion. This lateral gettering effect is suitable for the purification of transverse power devices