Electrically active defects in BF 2+ implanted and germanium preamorphized silicon

Abstract

Ultra-shallow p +-n junctions have been formed using 15 keV/10 15 cm −2 BF 2 + implantation into both Ge +-preamorphized and crystalline 〈1 0 0〉 silicon substrates. Rapid thermal annealing (RTA) for 15 s at 950°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 ( ΔC( 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, BF 2 + implantation along with RTA give rise to a depth distributed energy continuum which lies within the forbidden gap between E c - 0.13 eV and E c - 0.36 eV. From isothermal transient capacitance ( ΔC( 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 μm into the bulk.