Influence of fluorine preamorphization on the diffusion and activation of low-energy implanted boron during rapid thermal annealing

The diffusion and activation of low-energy implanted B in F preamorphized Si during rapid thermal annealing has been studied. Compared with low-energy B or BF2 implant into crystalline Si, low-energy B ion implantation into F preamorphized Si allows the formation of shallow junctions with reduced junction depth and increased B activation. F preamorphization suppresses the B transient enhanced diffusion in the low B concentration region resulting in a steep dopant profile which is necessary for shallow junction formation. Secondary ion mass spectroscopy and cross-sectional transmission electron micrograph results show F accumulation near the surface and at end-of-range defects. The interaction of F with defects is believed to reduce B diffusion in the low B concentration region. Low-energy B implant into F preamorphized Si followed by rapid thermal annealing has been demonstrated as a promising process for shallow junction formation.