Cross-sectional transmission electron microscope study of residual defects in BF+2-implanted (001)Si

A combined cross-sectional and plan-view transmission electron microscope study of residual defects in 110-keV, 5×1015/cm2 BF+2- implanted (001)Si has been carried out. Complete amorphization of the surface layer to a depth of about 1400 Å from the surface was found in as-implanted samples. The general trends of the amorphous/crystalline (a/c) regrowth were found to be similar in 550–900 °C annealed samples. ‘‘Paired’’ dislocations were observed in the first ∼600 Å of regrown layers. A high density of twins was found subsequently as the a/c interface advanced to the surface. Small defect clusters, irregular dislocations, equiaxial loops, and rodlike defects were observed to distribute in bands underneath the original a/c interface. The regrown layers were found to be almost dislocation- and twin-free in 1000–1100 °C annealed specimens. The regrown layer, however, contained a high density of fluorine bubbles. The bubbles were concentrated near the orignal a/c interface and the surface. Irregular dislocation networks were found to develop near the orignal a/c interface. The origins of residual defects and their possible influences on device applications are discussed.