Extended defects in ion-implanted si during nanosecond laser annealing

The formation of extended defects and their impact on dopant activation in nanosecond laser annealed silicon is investigated. It is found that laser anneal favours the formation of “unconventional” (001) loops (typically not expected to occur in ion implanted silicon). (001) loops are formed near the liquid-solid interface (in the non-molten side region). Following non-melt anneals, these loops act as scattering centres, leading to carrier mobility degradation. In contrast, in the case of melt anneals, the molten region itself is of excellent crystalline quality, free of any large defects and leads to very high activation rates. Full melting of the implanted region leads to an almost perfectly recrystallized layer. Finally, we demonstrate how the internal stress generated in silicon during ultra-fast laser annealing in the ns regime can modify the fundamental mechanisms of defect formation and lead to the formation of these “unconventional” loops.