Gettering by voids in silicon: A comparison with other techniques

A review of our recent work on gettering by voids formed by He ion implantation is presented. He bubble formation is a quite complex phenomenon and involves the interaction between several independent mechanisms. Its peculiarities are described and discussed. The void density, morphology and distribution have been studied as a function of He implanted energy, dose and annealing temperature. The results demonstrate the possibility to form, a narrow void layer at a controlled depth and with pre-determined void dimensions and density. The application of voids as gettering centres has been investigated by considering several methods. Processing temperatures higher than 1000 degrees C causes the release of trapped atoms but do not affect the gettering efficiency (as a difference with other gettering centres) so that a new segregation annealing allows to re-localise metals. The binding energy has been determined for many species (Pt, Cu, Fe) while other gettering properties (peak and total concentration) have been related to the void characteristics. The knowledge acquired demonstrates that voids can be successfully used as gettering centres in both conventional and proximity gettering procedures.