Modeling of Self-Interstitial Diffusion in Implanted Molecular Beam Epitaxy Silicon
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Modeling of self-interstitial diffusion in implanted molecular beam epitaxy silicon D. De Salvador1, A. Mattoni1, E. Napolitani1, A. V. Drigo1, S. Mirabella2, F. Priolo2 1 Dept. of Physics, University of Padova and INFM, Via Marzolo 8, 35131 Padova, ITALY 2 Dept. of Physics and Astronomy, University of Catania and INFM, Corso Italia 57, 95129 Catania, ITALY
ABSTRACT In this work a rate equations model describing the interstitials (I) diffusion in a trap containing medium is presented. The model takes into account the interstitial injection by implantation and annealing and the surface evaporation. We found an analytical approximated solution of the model which allows clarifying the interplay between the parameters involved and a simple comparison with experimental data obtained by the analysis of boron delta doping arrays broadening. The calculations allow to demonstrate that the I injected into the bulk and toward the surface at the end of the I clusters dissolution does not depend on the detailed time evolution of the I clusters, but only on the total amount of I produced by the implantation. The fitting of the experimental data allows to easily quantifying important physical parameters such as the I evaporation rate at the surface and the density of intrinsic interstitial traps. Applications of the model are shown in the case of MBE materials intentionally doped with substitutional C. The model successfully predicts the TED reduction by MBE intrinsic I-traps and allows to estimate the average composition of Interstitial-Carbon clusters.
INTRODUCTION The quantification of the number of silicon self interstitials (I) evolving inside a sample by implantation and subsequent annealing is a debated matter. This is a crucial problem since the interstitials regulate important physical processes such as the dopant transient diffusion and the formation of I-dopant and I-impurity clusters [1]. A proper description of the phenomena involves, in principle, the knowledge of many non-trivial physical processes: i) the dissolution dynamics of the I clusters produced by the implantation ii) the evaporation of interstitials through the surface iii) the interaction of the interstitials with dopants, with interstitial traps present in intrinsic MBE [2,3] silicon or with traps intentionally incorporated during growth (such as Carbon). In this work we will show a simple rate equation calculation which describes the evolution of a finite amount of interstitial generated by implantation and annealing just bellow the surface. The model, by introducing proper parameters, allows to calculate the amount of interstitials evaporating at the surface and the amount injected into the bulk. Moreover, the interaction of the interstitial with intrinsic traps characteristic of the MBE silicon will be taken into account. The model is tested on an MBE sample implanted with Si. Information about the interstitials
C5.6.1
population injected in the sample after annealing at 800 C is obtained by the SIMS analysis of the broadening of a B-delta doping
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