Electron Paramagnetic Resonance of the Lattice Damage in Boron-Implanted Intrinsic Silicon

The nature of the lattice damage in boron-implanted intrinsic silicon has been studied as a function of 140-keV 11B+ ion fluence using electron paramagnetic resonance (EPR). At most of the boron fluences, the observed EPR spectra consisted primarily of neutral 4-vacancies (Si-P3) and of unresolved E spectra (defects unknown). Concentrations (number/cm2) for the Si-P3 and Σ paramagnetic defects have been determined as a function of ion fluence for fluences ranging from 5 × 1012 to 1016 11B+/cm2. At the highest fluences the beginning of an isotropic resonance indicative of amorphous silicon was also observed. However, only a trace of the amorphous resonance was observed, and this resonance was found to be broadened and shifted to a lower magnetic field with a g value of 2.0071 instead of the usual 2.0055. Also observed at the higher fluences was the new anisotropic spectrum (labeled Si-SL3) arising from a defect having D2d symmetry. Finally, isochronal annealing studies indicate that the Si-P3 and Σ concentrations decrease toward zero by a 225° C anneal in a manner similar to that previously observed for oxygen-implanted-silicon. No paramagnetic defects were observed in the 600 to 900° C range. It is concluded that any electrical activity annealing in the 600 to 900° C range is primarily a result of a decrease in the number of compensating non-paramagnetic or diamagnetic defect centers.