Electrically active defects in BF2+ implanted and germanium preamorphized silicon

Ultra-shallow p(+)-n junctions have been formed using 15 keV/10(15) cm(-2) BF2+ implantation into both Ge+-preamorphized and crystalline [1 0 0] silicon substrates. Rapid thermal annealing (RTA) for 15 s at 950 degrees C was used for dopant electrical activation and implantation damage gettering. The electrically active defects present in these samples were characterized using Deep Level Transient Spectroscopy (DLTS) and isothermal transient capacitance (Delta C(t,T)). Two electron traps were detected in the upper half of the band gap at, respectively, E-c -0.20 eV and E-c -0.45 eV. They are shown to be related to Ge+ implantation-induced damage. On the other hand, BF2+ implantation along with RTA give rise to a depth distributed energy continuum which lies within the forbidden gay between E-c- 0.13 eV and E-c-0.36 eV. From isothermal transient capacitance (Delta C(t, T)), reliable damage concentration profiles were derived. They revealed that preamorphization induces not only defects in the regrown silicon layer but also a relatively high concentration of electrically active defects as deep as 3.5 mu m into the bulk. (C) 1998 Elsevier Science B.V.