Defects in <i>Q</i>-switched laser annealed silicon

Abstract

This paper describes the characterization of residual defects using transient capacitance spectroscopy for ion-implanted Si annealed with a Q-switched Nd-glass laser. The deep-level defect levels observed in this study were similar to those obtained in low-fluence ion implanted samples. The spatial distributions of deep-level defect concentrations were obtained for conditions using different anneal energy densities. From the difference of the distribution profiles, it is concluded that the greater the annealing laser energy densities, the lower the defect concentration near the junction.The reduction of the defect concentration is partly due to the inward movement of the junction. Thus the defects detected are those which lie further down in the tail of the defect distribution profile and have a lower concentration. Other reasons for the reduction of the defect concentration can be due to thermal annealing as heat propagates into the substrate during laser radiation. The reduction of the defect concentration agrees with the improvement of the measured I–V characteristics. Annealing with multiple shots of laser radiation was performed and the annealing model was established. The junction movement was confirmed by an electron beam induced conductivity technique. The carrier diffusion length measured in the region, where a surface layer of 2–3 μm was etched, decreases as the annealing energy density increases. This may be explained by the fact that the native defects generated thermally in the melts at the surface diffuse into the bulk and subsequently are trapped by the impurities in Si.