Characterization of BF2+ ion-implanted layers in strained-silicon/SiGe heterostructures

BF2+ implanted strained silicon/SiGe was characterized with the aim of maximizing the performance of strained-silicon pMOSFETs. Recovery of implantation damage in the strained-silicon layer was achieved by annealing at 900 °C or higher, but end-of-range defects remained in the SiGe layer after annealing. Germanium recoil and vacancy-enhanced redistribution of germanium caused by BF2+ implantation are not negligible issues in strained-silicon MOSFET fabrication. Boron diffusion during annealing was retarded in SiGe compared to that in silicon, and as a result, a higher-concentration and shallower boron-doped region than that in silicon can be formed in strained silicon/SiGe. Hole mobility in boron-doped strained silicon is about 30% higher than in silicon. These results suggest that lower source and drain resistance can be achieved in the strained-silicon pMOSFET than in the silicon pMOSFET.