A SLOW POSITRON BEAM STUDY OF VACANCY FORMATION IN FLUORINE-IMPLANTED SILICON

The subsurface vacancy profile in Czochralski (Cz) Si (100) implanted to a dose of 2 X 10(14) cm-2 with 120 keV fluorine ions has been determined using a slow positron beam. The unique sensitivity of the positron technique to vacancy concentrations of part per million (ppm) order is utilized. We demonstrate the presence of vacancies at ppm concentrations at depths up to 1 mum greater than the depth predicted by Monte Carlo modeling. The vacancies caused by the implantation process are suggested to consist of an immobile and a mobile component, the latter component being able to diffuse to such depths.