The defect profile induced by F ion implantation (120 keV, 2×10¹⁴/cm²) into a Czochralski (Cz)-Si wafer was determined by analysis using a slow positron beam method. It was proved that vacancies were present at ppm concentrations at depths exceeding 1.5μm, far beyond the depth to which F ions were implanted. The induced defects consisted of at least two components which could be correlated with their depth.: Annealing at 300°C extinguished the defects only in the deeper region and annealing at 600°C extinguished those in the ion implanted region. It was, further, confirmed that the use of an improved Monte-Carlo-deduced positron implantation profile was better than that of the Gaussian derivative one in calculating defect profiles.