MODELING INACTIVE BORON DURING PREDEPOSITION PROCESSES

A new type of boron cluster is presented through the study of boron di ffusion at high concentrations under predeposition conditions. Recent experimental results of boron predeposition give the opportunity to an alyze, with the simulations, the behavior of the inactive part of the boron profile, found to increase dramatically with surface concentrati ons. After a rapid thermal annealing, the electrical activation appear s to be extremely high due to the dissolution of the inactive part of the profile. The only way to reproduce the experimental observations h as been to consider an inactive and mobile 2-atom boron cluster. A com plete kinetic model, including the reactions between boron cluster, bo ron-interstitial pair, substitutional boron and point defects, is used in order to determine all the parameters characterizing this cluster. The diffusivity of the cluster is much less than the one of the boron -interstitial pair (about 4b times). It is suggested that the nature o f this cluster may depend on the exact predeposition conditions. Final ly, from a general point of view, the behavior of supersaturations of interstitials during predeposition as a function of surface concentrat ion is presented, in order to understand the implication of each basic reaction involved in the kinetic model.