Defects in oxygen-implanted silicon-on-insulator structures probed with positrons

Defects in a silicon-on-insulator structure formed by high-energy (200-keV) oxygen implantation has been studied utilizing a variable-energy positron beam. The positron-based probe is found to be especially sensitive to the condition of the top Si layer. Open-volume defects (cavities) are detected in the top 80-nm Si layer in the as-irradiated state. The majority of these defects are removed by high-temperature annealing (1300°C) after which the positron response correlates with the density of dislocations observed by transmission electron microscopy. Variations in dislocation density across a wafer were probed with positrons, demonstrating the potential of positrons in defect topology.