Radiation effects on the behavior of carbon and oxygen impurities and the role of Ge in Czochralski grown Si upon annealing

Abstract

The annealing behavior of the oxygen and carbon impurities in Czochralski grown silicon (Cz-Si) was investigated in electron- and neutron-irradiated materials. The irradiated samples were subjected to isochronal anneals of up to ∼1000 °C, and the evolution of oxygen and carbon concentrations was monitored by means of infrared spectroscopy from the amplitudes of the 1106 and 605 cm−1 bands of the two impurities correspondingly. It was found that the electron irradiation does not affect the temperature of annealing of oxygen, although in the neutron-irradiated samples the oxygen band begins to decay in the spectra at a lower temperature than that in the nonirradiated samples. This behavior could be determined by supersaturation of vacancies mainly liberated from disordered regions in the latter material. This assists the oxygen aggregation process. Regarding carbon evolution, it was found that in the irradiated samples the annealing out of the 605 cm−1 band occurs at a lower temperature than that of the nonirradiated samples. Prior to the onset of decay of the 605 cm−1 band an inverse annealing stage was observed in the irradiated samples, indicating partial restoration of substitutional carbon. The general behavior was discussed with respect to the supersaturation of intrinsic defects, mainly self-interstitials. As a result, large CN(SiI)M complexes are formed. There are two processes running in parallel: the recovery of substitutional carbon from carbon-related defects and CN(SiI)M complexes and the transformation of CN(SiI)M complexes to SiC-based precipitates. Noticeably, in electron-irradiated Ge-doped Si the inverse annealing stage of substitutional carbon is suppressed. Furthermore, our results showed that the Ge doping of Cz-Si of up to 2×1020 cm−3 does not practically affect the temperature at which oxygen and carbon are completely lost in irradiated Cz-Si:Ge.