Role of silicon surface in the removal of point defects in ultrashallow junctions

The role of the Si surface in the annihilation of point defects has been studied for ultrashallow 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 BF2 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. © 1996 American Institute of Physics.