Defects Induced by Helium Implantation: Impact on Boron Diffusivity
- PDF / 774,925 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 80 Downloads / 198 Views
E7.4.1
Defects induced by Helium implantation: Impact on Boron diffusivity F. Cayrel1, D. Alquier1, C. Dubois2 and R. Jerisian1 1
Université de Tours, L.M.P, 16, rue Pierre et Marie Curie, B.P. 7155, F37071 TOURS Cedex, France 2
L.P.M. - INSA Lyon, 20 rue A. Einstein, F-69621 Villeurbanne Cedex, France.
ABSTRACT High dose helium implantation followed by a suitable thermal treatment induces defects such as cavities and dislocations. Gettering efficiency of this technique for metallic impurities has been widely proved. Nevertheless, dopants, as well as point defects, interact with this defect layer. Due to the presence of vacancy type defects after helium implantation, boron diffusion can be largely influenced by such a buried layer. In this paper, we study the influence of helium induced defects on boron diffusion. The boron diffusion in presence of these defects has been analyzed as a function of different parameters such as distance between boron profile and defect layer and defect density. Our results demonstrate that the major impact known as boron enhanced diffusion can be partially or completely suppressed depending on parameters of experiments. Moreover, these results clarify the interaction of boron with extended He-induced defects.
INTRODUCTION The Semiconductor Industry Association (SIA) roadmap has fixed the limit for the metallic concentrations by 1010 at.cm-2 in 2009 for the new device generation. This major concern has led to the development of various techniques dedicated to remove metallic impurities from device active regions in order to trap them intentionally on introduced gettering sites, within the bulk or at the backside of the wafers [1, 2]. Helium implantation in silicon, when followed by an adequate annealing, leads to the formation of a band of extended defects able to trap metallic impurities. Its efficiency has been widely proved on various metals: Au, Cu, Ni, Fe, Pt [3-5]. However, this defect band containing both types of defects (interstitial and vacancy type) strongly interacts not only with metal but also with dopants or point defects. In previous works, we have already demonstrated that dopant segregation occurred within the defect band [6, 7]. Moreover, Raineri et al. have shown that cavities in silicon are efficient for gettering of interstitials and have demonstrated that they could decrease or even suppress interstitials extended defects due to implantation damage [8]. Nevertheless, the impact of cavities on dopant diffusion has been poorly studied [9, 10]. By introducing a vacancy type defect, He implantation modifies the local point defect equilibrium. Therefore, there is a great interest in studying boron diffusion in presence of cavities. In this paper, we will present boron diffusion experiments in presence of defects induced by helium implantation for various doses or energies. Experiments have been specially prepared to analyze the influence of these defects on boron diffusion depending
E7.4.2
on the distance between the boron profile and the defect band and also d
Data Loading...
