CHARACTERIZATION OF VACANCY-LIKE DEFECTS IN BORON-IMPLANTED SILICON WITH SLOW POSITRONS

Vacancy-like defects in Si after boron implantation were studied by me ans of slow positrons. Ion implantation was carried out at 300 K subse quently with 3 energies to obtain a wide, homogeneously damaged layer. The width of the defect profiles increases with the ion dose and is i n good agreement with Monte-Carlo simulations (TRIM-92), The defect pr oduction rate was similar to root N, where N is the boron fluence. Thi s behavior is typical for defect formation via homogeneous nucleation. The divacancy concentration observed by infrared absorption was nearl y constant after boron implantation, whereas the overall concentration of vacancy-like defects and the S-parameter in the implanted layer in crease. This led to the conclusion that the divacancy is dominated by another defect of larger volume in highly boron-implanted Si. The samp les were annealed in-situ up to 1150 K. The annealing behavior depends on the implantation dose and on the sample material (i.e. FZ- or Cz-S i). An annealing stage at 725 K was found in all samples. A decrease o f the S-parameter below the value obtained for defect-foe Si was obser ved in Ct-Si only after annealing at 750 K. This must be attributed to the formation of oxygen-vacancy complexes. An increase of the S-param eter above the defect value at room temperature was observed in a regi on 100 nm below the surface for high boron fluences after annealing at 650 K.