GETTERING OF METALS BY VOIDS IN SILICON

The gettering efficiency of copper and platinum by cavities formed in silicon after high dose helium implantation and thermal processing has been investigated. The formation of helium bubbles and their evolutio n into cavities has been investigated by transmission electron microsc opy; the measured values of void density, diameter and the width of th e void layer can be interpreted by assuming, a simple coalescence mode l. Metal impurities intentionally introduced in silicon by ion implant ation are efficiently gettered inside these cavities, probably due to the large amount of unsatured bonds at the void internal surface. Proc essing at temperatures higher than 1000 degrees C causes a release of the trapped metal atoms which can be gettered again by repeating the p rocess. The method is demonstrated on real devices such as large area diodes (a particle detector) and bipolar transistors. The capability t o localize in depth and across the wafer surface on the gettering site s allows the development of a new gettering engineering. (C) 1995 Amer ican Institute of Physics.