Influence of the initial boron doping level on the boron atom distribution arising as a result of heat treatment in silicon implanted with boron ions

The dependence of the boron distribution on the initial boron concentration in the range (1–9)×1019 cm−3 was investigated by secondary-ion mass-spectrometry (SIMS) after heat treatment of boron-ion implanted silicon at 900 °C. It was found that when the initial boron concentration exceeds the solubility limit at the annealing temperature used, two additional peaks arise in the boron concentration profiles at the boundaries of the ion-implantation disordered region. It is suggested that their appearance in these regions at high doping levels is due to clustering of excess interstitial impurity atoms not built into the lattice sites following displacement of boron atoms from the lattice sites by intrinsic interstitials that leave the disordered region.