Interactions between dopants and point defects during nitridation processes

The effective diffusivity of substitutional impurities in silicon is reconsidered by involving the point defects. Four basic reactions, including the interstitials and vacancies contributions, are necessary to derive a general formulation of the effective diffusion coefficient. The model has been fitted to data on arsenic diffusion in silicon under nitridation conditions, with a very good agreement. From these experimental results, it has been deduced that arsenic diffuses mostly by a vacancy mechanism with a partial interstitial contribution, which cannot be neglected. It has been also observed that, under these experimental conditions, the point-defects concentrations are a complex function of the observed phosphorus and antimony diffusivities, in contrast with previous approaches. The general behavior of the dopants diffusivities as a function of point-defects concentrations is also presented. This allows the importance of each reaction involved in this analysis to be shown clearly. Finally, the recombination of point defects mediated by dopants pairs has been emphasized over a wide range of conditions for point-defects concentrations.