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 be en studied for ultrashallow p(+)/n junctions. The dopant and defect di stributions for low-energy implants lie within a few hundred angstroms of the surface. The proximity of the Si surface has been shown to hel p in the efficient removal of point defects for the shallower junction s. A 5 keV, 1 x 10(15) cm(-2) BF2 implant and a 30 keV, 3.3 x 10(14) c m(-2) BF2 implant were estimated to create comparable damage at differ ent 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 t he point defect distribution was closer to the surface, was defect fre e. This is attributed to the role of the Si surface as an efficient si nk for the removal of point defects. (C) 1996 American Institute of Ph ysics.