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 sam ples were characterized using Deep Level Transient Spectroscopy (DLTS) and isothermal transient capacitance (Delta C(t,T)). Two electron tra ps 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+ impl antation-induced damage. On the other hand, BF2+ implantation along wi th RTA give rise to a depth distributed energy continuum which lies wi thin the forbidden gay between E-c- 0.13 eV and E-c-0.36 eV. From isot hermal transient capacitance (Delta C(t, T)), reliable damage concentr ation profiles were derived. They revealed that preamorphization induc es 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.