Impact of gettering by helium implantation on boron and iron segregation

¹ LMP, 16 rue Pierre et Marie Curie, BP 7155, 37071 Tours Cedex, France
² STMicroelectronics, 16 rue Pierre et Marie Curie, BP 7155, 37071 Tours Cedex, France

Corresponding author: alquier@univ-tours.fr

Received: 23 May 2002
Revised: 7 January 2003
Accepted: 7 April 2003
Published online: 27 June 2003

Abstract

The use of gettering techniques that can be precisely localized in the component, such as neutral element implantation, has become crucial for power device manufacturing. High-dose helium implantation in silicon with a subsequent annealing induces defects (cavities and dislocations) which are able to getter metallic impurities and interact with dopants. These interactions can become a drawback of this technique. In this work, Si wafers -oriented, p-doped with a concentration in between 6 × 10¹⁴ and 8 × 10¹⁸ B/cm³, were used. Iron contamination was performed by backside implantation (100 keV and 10¹² Fe cm⁻²). Helium implantation was performed at 40 keV and 5 × 10¹⁶ at cm⁻² at room temperature and followed by a Furnace Annealing (FA) stage. Secondary Ion Mass Spectrometry (SIMS) was used to study the dopant/metal/cavity layer system. In this paper, we will focus on the cavity layer interactions with both metals and dopant impurities. Our experimental results exhibit a large segregation of both species within the cavity layer that occurs during the annealing stage. Both species segregate simultaneously in helium-implanted samples without interacting one to the other. The number of gettering sites does not limit the trapping reactions.