Ion-beam-induced damage in silicon studied using variable-energy positrons, Rutherford backscattering, and infrared absorption

Silicon (100) wafers have been irradiated at 300 K with silicon ions or helium ions at energies between 0.2 and 5.0 MeV. Fluences ranged from ${10}^{11}$ to ${10}^{16}$ ${\mathrm{cm}}^{\mathrm{-}2}$. The associated defect profiles have been analyzed using variable-energy positron-beam methods. Displaced-atom distributions have been extracted from Rutherford-backscattering-channeling (RBSC) measurements and supplemented by infrared (1.8 μm) absorption measurements to yield divacancy concentrations. Defect annealing is observed through the divacancy anneal stage (∼470 to 570 K), He-irradiated silicon returning to single-crystal quality as measured by infrared and positron methods. For the same anneal, Si-irradiated silicon shows partial restoration of crystallinity (RBSC), no change in positron-trapping characteristics, and removal of the optically active divacancies. Annealing to between 870 and 970 K restores the crystal to near preimplant characteristics.