Direct high-resolution determination of vacancy-type defect profiles in ion-implanted silicon

The depth distribution of open-volume point defects created by room temperature implantation of Cz silicon by 100 keV B+ ions at a dose of 5 × 1014 cm−2 has been determined by enhanced-resolution beam-based positron annihilation spectroscopy (PAS). By incremental controlled etching (via anodic oxidation of 50–100 nm layers) the depth resolution of the PAS is maintained at ~50 nm by using positrons implanted at energies below 2 keV to probe each layer as it brought close to the surface by the etching process. The etch depths have been verified by using secondary-ion mass spectrometry to profile the boron depth distribution. The results are in good agreement with Monte Carlo simulations, particularly in the traditionally difficult-to-measure deep tail region.