Observation of point defect injection from electrical de-activation of arsenic ultra-shallow distributions formed by ultra-low energy ion implantation and laser sub-melt annealing

The stability and the evolution of electrical properties of high concentration arsenic ultra-shallow junctions in sili-con have been studied with regard to their effect on the evolution of point defects. The activation of 2 keV 1x1015 cm-2 As implants was performed using millisecond sub-melt laser annealing at two different temperatures, 1100° and 1300 °C. The electrical deactivation upon subsequent thermal treatment at 700°C was indirectly monitored through the diffusion of five 10 nm-wide boron layers aimed to detect the injection of self-interstitials coming from dopant clustering. Thermal treatments were repeated on samples implanted with Ge at condition similar to the As ones. The comparison helped to discriminate between interstitials coming from lattice damage evolution and do-pant clustering. The results show the relevance of the laser annealing temperature in order to ensure junction stability in terms of active carrier concentration and junction depth.