Sub-millisecond (ms) non-melt laser annealing (NLA) is investigated through experiments and atomistic KMC modeling.NLA can improve the dopant activation dramatically and achieve shallow junctions. B diffusivity during sub-ms annealing is discussed for the first time. Our KMC model with F n V m complexes indicates that the thermal budget of sub-ms annealing is too small for full defect evolution and one possible solution for defect stabilization is F co-implant.