Strain behavior and dopant activation of heavily in-situ B-doped SiGe epitaxial films treated by nanosecond laser annealing

Heavily doped epitaxial films with an active dopant concentration over 1 × 10²¹/cm³ in the source/drain regions are key requirements for advanced metal-oxide-semiconductor field-effect transistors (MOSFETs) with ultralow contact resistance. In this study, we investigated the microstructure, strain characteristic, and electrical property with dopant behavior of heavily in-situ B-doped (ISBD) SiGe films (chemical B concentration >3 × 10²¹ atoms/cm³) treated by nanosecond laser annealing (NLA). The lattice parameters of the B-doped SiGe films considerably decreased in the regrown regions because of increased substitutional B concentrations. The substitutional B atoms decreased the accumulated strain energy per unit area of the regrown regions, leading to epitaxial regrowth of B-doped SiGe film without strain relaxation. Additionally, electrical analyses demonstrated that the active B concentrations in the regrown regions increased above 3 × 10²¹ atoms/cm³. In the unmelted region, the active B concentrations were close to that of the as-grown film, which was similar to the relative ratio of the active and inactive states in the B 1s spectra measured through X-ray photoelectron spectroscopy (XPS). Our results revealed that nonsubstitutional B atoms in the as-grown heavily ISBD SiGe films were converted into substitutional B atoms and activated in the recrystallized region via NLA.