Formation, evolution and annihilation of interstitial clusters in ion implanted Si

Abstract

Formation, thermal evolution and annealing kinetics of self-interstitial clusters in ion implanted Si have been investigated. Deep level transient spectroscopy measurements performed on epitaxial and Czochralski Si samples implanted with Si ions at energies of 145 keV or 1.2 MeV reveal that these clusters are formed for fluences above 10 12/cm 2 and annealing temperatures higher than 550°C. Interstitial clusters introduce seven well defined levels in the Si band gap at E V + 0.33 eV, E V + 0.52 eV, E C − 0.58 eV, E C − 0.50 eV, E C − 0.37 eV, E C − 0.29 eV and E C − 0.14 eV. Analysis of the annealing kinetics at temperatures in the range 550–700°C reveal that the clusters undergo Ostwald ripening and anneal out with a characteristic dissociation energy of ∼2.3 eV for a Si fluence of 1 × 10 12/cm 2. Furthermore, their annealing temperature increases with implantation fluence. These results indicate that small interstitial clusters act as the source of interstitial supersaturation that drive transient enhanced dopant diffusion in the absence of extended defects.