Electron paramagnetic resonance of the lattice damage in oxygen-implanted silicon

Abstract

The nature of the lattice damage produced at room temperature in ion-implanted intrinsic and n-type silicon has been studied as a function of 160-keV O+ ion fluence using electron paramagnetic resonance (EPR). The known EPR spectra observed were the negative divacancy (Si-G7), the neutral vacancy-oxygen (Si-S1), the neutral 4-vacancy (Si-P3), and the isotropic resonance at g = 2.0055 which is indicative of amorphous silicon. In addition, a new spectrum, labeled Si-S2, was observed which may be the negative 4-vacancy. Concentrations (number/cm2) for the various paramagnetic defects were determined as a function of ion fluence for fluences ranging from 1010 to 1017 O+/cm2. From these measurements we conclude that the lattice damage produced in crystalline silicon by individual ions whose maximum calculated energy density into atomic processes is ≲ 15 eV/Å ion consists of simple defects such as observed in electron- and neutron-irradiated silicon. Furthermore, overlap effects in the lattice damage produced by ion implantation are small providing the maximum energy density into atomic processes is ≲ 1.5 × 1019 keV/cm3. For energy densities into atomic processes between ∼ 1.5 × 1019 and ∼ 1021 keV/cm3, there appears to be an accumulation of defect complexes which are characterized by a high concentration of defects whose electrons tend to be delocalized among the defects within the complex. Finally, our measurements indicate that ∼ 1021 keV/cm3 of energy into atomic processes must be accumulated in the form of lattice damage in order to convert crystalline silicon to the amorphous state.