Elemental B distributions and clustering in low-energy B+ ion-implanted Si

A detailed study is presented of characteristic elemental B distributions in Si produced by low-energy B+ ion implantation and annealing. Implant concentration profiles have been determined with approximately nanometer spatial resolution using energy-filtered imaging in the transmission electron microscope, for a B+ ion dose close to those relevant to electronic device processing. It is demonstrated that, for as-implanted Si, the near-surface B distribution shows a smooth concentration peak which correlates well with theoretical simulation and shows no anomalous surface buildup of the type generally indicated by secondary ion mass spectrometry measurements. After annealing of the layers, the present direct observations reveal that the final B distribution is characterized by residual nanometer-scale elemental clusters which comprise disordered zones within the restructured Si lattice.