Retarded and enhanced dopant diffusion in silicon related to implantation-induced excess vacancies and interstitials

Abstract

The influence of the lattice defects induced by silicon-ion implantation on the B, P, As, and Sb diffusivities is investigated after annealing between 700 and 900 °C. The nature and depth position of the residual implantation defects in undoped samples is determined by the analysis of the rocking curves obtained by triple-crystal x-ray diffraction and transmission electron microscopy. In particular, besides the interstitial dislocation loops and clusters below the original amorphous-crystal interface, the epitaxial regrowth of the amorphized silicon leaves a vacancy-rich surface layer and a deeper region enriched in interstitials. These regions correspond to those where Monte Carlo simulations of defect production foresee excess point defects. Accordingly, as the dopant is located in correspondence with the vacancy or interstitial clusters, different behaviors of anomalous diffusion are observed. In the deep region where an interstitial excess is present, B and P show marked enhanced diffusion, while only a small enhancement is exhibited by As and Sb. On the contrary, retarded diffusivity for B and light enhancement for As and Sb are observed in the surface layer. These different trends are consistent with the different accepted contributions of vacancies and interstitials to the diffusion mechanisms of the investigated dopants.