Role of silicon surface in the removal of point defects in ultra-shallow junctions

The role of the Si surface in the annihilation of point defects has been studied for ultra-shallow p⁺/n junctions. The dopant and defect distributions for low energy implants lie within a few hundred Angstroms of the surface. The proximity of the Si surface has been shown to help in the efficient removal of point defects for the shallower junctions. A 5 keV, 1×10¹⁵ cm^-2 BF ₂ implant and a 30 keV, 3.3×10¹⁴ cm^-2 BF₂ implant were estimated to create comparable damage at different depths. After identical anneals, the higher energy implant sample showed end-of-range dislocation loops in cross-sectional transmission electron microscopy analysis, while the low energy sample, for which the point defect distribution was closer to the surface, was defect-free. This is attributed to the role of the Si surface as an efficient sink for the removal of point defects