Boron activation and redistribution during thermal treatments after solid phase epitaxial regrowth

The solid phase epitaxial regrowth (SPER) technique achieves active B concentrations up to a few times 1020 cm−3 after low-temperature recrystallization process, while higher B concentration regions remain immobile forming electrically inactive B clusters during SPER. Kinetic Monte Carlo simulations on B diffusion and activation in preamorphized Si during annealing after SPER are presented, providing a good insight into mechanisms that drive these phenomena. Simulations show that the presence of end of range (EOR) defects, still present beyond the amorphous/crystalline interface after recrystallization, leads to additional deactivation during subsequent anneal treatments. Moreover, B uphill diffusion towards the surface is observed in the medium concentration region, while downhill diffusion occurs in the tail region of the B profile. During prolonged anneals B activation decreases until it reaches a minimum, which becomes lower as the annealing temperature reduces. Finally, when EOR defects dissolve or reach very stable configurations such us dislocation loops, B reactivation is observed as well as B tail diffusion.