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 dev ice areas, Cavities have been obtained by helium implantation (5 x 10(16) H e+/cm(2), 40 keV) followed by a thermal treatment on samples previously con taminated 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 degreesC for several minutes in a neutral ambience (N-2). The metallic distribution has been monitored in each activ e device area by using current versus voltage and deep level transient spec troscopy techniques (DLTS). A symmetrical distribution of metallic impuriti es and current values has been observed in each active region. The influenc e of cavities extends laterally to several millimeters depending on the tem perature and time of diffusion, This lateral gettering effect is suitable f or the purification of transverse power devices, (C) 2001 Elsevier Science B.V. All rights reserved.