Ion Beam Injected Point Defects in Crystalline Silicon: Migration, Interaction and Trapping Phenomena

Our recent work on the room temperature migration and trapping phenomena of ion beam generated point defects in crystalline Si is reviewed. It is shown that a small fraction (∼ 10−6) of the defects generated at the surface by a shallow implant is injected into the bulk. These defects undergo a long range trap-limited diffusion and interact with both impurities, dopants and preexisting defects along their path. In particular, these interactions result in dopant deactivation and/or partial annihilation of pre-existing vacancy-type defect markers. It is found that in highly pure, epitaxial Si layers, these effects extend to several microns from the surface, demonstrating a long range migration of point defects at room temperature. By a detailed analysis of the experimental evidences we have identified the Si self-interstitials as the major responsible for the observed phenomena. This allowed us to give a lower limit of 6×10−11-cm2/s for the room temperature diffusion coefficient of the Si self-interstitials. Room temperature trap-limited migration of vacancies is also detected as a broadening in the divacancy profile of as implanted samples. In this case the room temperature diffusion coefficient of vacancies has been found to be ≥3 × 10−12 cm 2/s. These data are presented and their implications discussed.