Characterization of incomplete activation of high-dose boron implants in silicon

The incomplete activation observed when high doses of boron (2×1015−2×1016 ions/cm2) are implanted in silicon is characterized by a maximum concentration of electrically active boron that is independent of both the dose and anneal time and well below the solid solubility value. An Arrhenius plot for this concentration-temperature dependence yields an activation energy of 0.31 eV. It is suggested that the incomplete activation is due to interactions between the implanted ions. Whether the defect structure is a simple B–B pair or a cluster involving residual damage is not clear at this time.