DAMAGE-DEPENDENT ELECTRICAL ACTIVATION OF ION-IMPLANTED SILICON .1. EXPERIMENTS ON PHOSPHORUS IMPLANTS

The electrical activation mechanism of phosphorus ions implanted into a silicon substrate is studied during low-temperature (≈550°C) annealing. Apparently anomalous behavior where the electrically active fraction versus dose curve shows a peak in a limited dose range is analyzed by measuring the distribution profiles of damage and carrier concentration. Carrier generation was found to be strongly influenced by the extent of damage in the layer. Phosphorus atoms in layers with less than 20% damage were not electrically activated. However, in layers with more than 20% damage, electrical activation abruptly increased with the change of damage. This correlation existed at each depth in the substrate for all samples with various doses. The anomalous dose dependence of the electrically active fraction was recognized to be an integral result of the phenomenon. Analysis of the damage formation showed that overlapping of amorphous clusters produced in each ion trajectory is essential for the electrical activation of implanted impurities. This is related to the carrier compensation center which might be formed after recovery of the amorhpous clusters.