Defect evolution in Co-implanted Si during annealing at 1000 °C studied using variable-energy positrons and Rutherford backscattering

Variable-energy positron-annihilation spectroscopy (PAS) and Rutherford backscattering channeling (RBSC) have been used to probe damage induced by the implantation of n-type CzSi with Co+ ions at 375 °C to fluences ranging from 2×1014 to 1×1016 cm-2. For fluences of 2×1014 and 1×1015 cm-2 only one type of defect was detected using the positron technique, distributed evenly to a depth of 1 μm, ∼2.5 times that of the implanted ions. For fluences between 4×1015 and 1×1016 cm-2 a second defect type was observed, to a depth equal to the range of the implanted ions. These defects have been tentatively identified as vacancy-impurity complexes and vacancy clusters, respectively. No defects were detected using Rutherford backscattering channeling for the samples irradiated to fluences of 2×1014 and 1×1015 cm-2; however, defects were observed for the higher fluences. Upon annealing of the samples irradiated to these higher fluences at 1000 °C for 1 min, large cavities (>1 nm) were detected using PAS. This is consistent with the dissolution of silicide precipitates previously observed using TEM. It is suggested that the formation of the cavities is dependent on the presence of vacancy clusters following the ion implantation. The evolution of the cavities at 1000 °C was observed for longer annealing times. An increase in the number of extended defects was observed using RBSC following annealing to 1000 °C. © 1996 The American Physical Society.