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Atomistic simulations of extrinsic defects evolution and transient enhanced diffusion in silicon A. Claverie, B. Colombeau, F. Cristiano*, A. Altibelli and C. Bonafos Ion Implantation Group, CEMES/CNRS, BP 4347, F-31055 Toulouse Cedex 4 * LAAS/CNRS, 7 Avenue du Colonel Roche, F-31077 Toulouse Cedex ABSTRACT We have implemented an atomistic simulation of the Ostwald ripening of extrinsic defects (clusters, {113}’s and dislocation loops) which occurs during annealing of ion implanted silicon. Our model describes the concomitant time evolution of the defects and of the supersaturation of Si interstitial atoms in the region. It accounts for the capture and emission of these interstitials to and from extrinsic defects (defined by their formation energy) of sizes up to thousands of atoms and includes a loss term due to the interstitial flux to the surface. This model reproduces well the dissolution of {113} defects in Si implanted wafers. We have subsequently studied the characteristics of TED in the case of B implantation at low and ultra low energy. In such cases, the distance between the defect layer and the surface plays a crucial role in determining the TED decay time. The simulations show that defect dissolution occurs earlier and for smaller sizes in the ultra-low energy regime. Under such conditions, TED is mostly characterized by its "pulse" component which takes place at the very beginning of the anneal, probably during the ramping up. In summary, we have shown that the physical modelling of the formation and of the growth of extrinsic defects leads to a correct prediction of the "source term" of Si interstitials and at the origin of TED.

INTRODUCTION The predictive simulation of dopant diffusion is essential for the controlled reduction of the dimensions of future IC’s. Among other dopants, boron certainly deserves special attention not only because of its technological importance but also because its diffusive behavior has been much more experimentally studied than any other impurity and thus a reliable set of data exists. There are two distinct components in the anomalous diffusion of boron in Si. On one hand, for both high concentrations of B and Si interstitial atoms, boron-Si interstitial clusters (BIC’s) are formed and tend to immobilise a fraction of B. On the other hand, the coupling of free-interstitial Si atoms with (probably) substitutional boron atoms enhances B diffusivity by a factor which is proportional to the supersaturation of Si(int)’s in the region. Thus, describing and modelling the transient enhancement of diffusivity that boron encompasses during annealing only requires the knowledge of the time and space evolution of the Si(int)’s supersaturation in the region where B stands and this, at the given temperature. This supersaturation initially results from the injection of Si atoms in the crystal during ion implantation and/or dopant activation. Upon annealing, these Si atoms condense to form defects of various types which, when large enough, can be detected by TEM. Earlier works have ascr