A Physically Based Modeling of Boron TED in Amorphised Si

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A Physically Based Modeling of Boron TED in Amorphised Si Evelyne Lampin, Vincent Senez and Alain Claverie1 IEMN - Dpt. ISEN B.P.69, 59652 Villeneuve d’Ascq Cedex, France 1 CEMES - CNRS BP 4347, 31055 Toulouse Cedex, France ABSTRACT We have developed a physically based modeling of TED of implanted boron in amorphised Si. The simulation starts with a supersaturation of Si free interstitials located below the amorphous/crystalline interface which, upon annealing, tend to diffuse out or to precipitate in the form of extended defects (clusters, {113}s, dislocation loops). The modeling of the nucleation and growth of these defects is divided into three distinct stages: the nucleation, the "pure growth" and the Ostwald ripening. This system can interact with a surface (characterized by a given recombination velocity for Si interstitials) only after the SPE regrowth is completed. Implementation of this model into a process simulator allows to describe the isothermal and isochronal evolutions of the sizes and of the densities of dislocation loops in agreement with TEM observations. Assuming that boron diffusion is caused by the concomitant time and space variations of the free interstitial supersaturation in the wafer, TED can be accurately predicted for a variety of experimental conditions. INTRODUCTION Transient enhanced diffusion (TED) of boron implanted into crystalline and preamorphised silicon has been often related to the presence of extended defects [1],[2]. Depending on ion dose, energy and annealing conditions, different types of extended defects are observed: clusters, {113}s, faulted and perfect dislocation loops. Boron TED and the formation of extended defects have been proposed [3] to have the same origin: the thermal behavior of the silicon selfinterstitials atoms (Si(int)s) created in high supersaturations by the ion implantation. Upon annealing, a large part of the Si(int)s precipitate into extended defects while the remaining free Si(int)s couple with the boron atoms and make them diffuse through the Kick-out mechanism. In the present study, we expose a modeling of boron TED based on the description of the nucleation and growth of extended defects through three stages: the nucleation, driven by a decrease of the free energy, the "pure growth" where the defects mostly act as sinks for the remaining free Si(int)s, and the Ostwald ripening where the defects act as sources and sinks and evolve in dynamical equilibrium with the free Si(int)s. This model is implemented into a process simulator [4] to describe the evolutions of the sizes and densities of the dislocation loops. The concomitant time and space variations of the free Si(int) supersaturation in the wafer is used to calculate the boron profiles in a standard "five-species" model [4] of the interactions between dopants and point defects. The characteristics of the extended defects and of boron diffusion are compared to a complete set of experimental data obtained by TEM and SIMS.

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MODELING The nucleation of extended defects is driven by the de

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