Interaction and migration properties of ion beam induced point defects in crystalline silicon: Basic research and technological relevance

A comprehensive understanding of point defect properties in crystalline Si is required in order to elucidate and control dopant diffusion. In this paper we will review several experiment assessments of the migration and agglomeration phenomena of ion beam generated defects. In our approach electrical methods (using spreading resistance profiling and deep levels transient spectroscopy) are used to monitor room temperature transport properties of point defects. It is found that both self-interstitials and vacancies undergo fast long range migration which is interrupted by trapping at impurities (O, C) or dopant atoms. In a highly pure (low C, low O content), lightly doped epitaxial Si, ion generated defects can freely migrate for as much as 3 divided by 5 mu m before being trapped. A lower limit of 10(-10) cm(2)/s and 6x10(-12) cm(2)/s has been found for the diffusion coefficients of interstitials and vacancies respectively. These data are compared with theoretical calculation of the point defect migration properties. Furthermore, we show that the sample surface acts as a very effective sink for the migrating defects at room temperature. All the data clearly show that point defect interaction with impurities and pre-existing defects compete with the defect-dopant interaction that drives dopant diffusion. We have also explored a technological application of this finding: in particular transient enhanced diffusion of shallow boron implants is shown to be significantly reduced in the presence of surface damage induced by a plasma etching process.