Electronic Defect Levels in Ultra-Shallow p+n-Junctions Formed by Low-Energy B Ion Implantation into Ge-Preamorphized Silicon

Abstract

Ultra-shallow p+n-junctions were formed by low-energy boron implantation into n-type monocrystalline silicon preamorphized with germanium. The boron implantation was performed at 3 keV and 1015 cm-2. The crystallization and the electrical activity were obtained by rapid thermal annealing (RTA) at a control thermocouple setting of 950° C for 15 s. In this work, the electrical defects induced by this process were characterized by isothermal transient capacitance (ΔC(t, T)) measurements and deep level transient spectroscopy (DLTS). The electron emission spectrum is dominated by two kinds of defects. The first is classical and is represented by two discrete levels related to germanium implantation. The second, observed for the first time in such structures, seems to be an energy distributed continuum located between 0.18 eV and 0.33 eV below the conduction band edge. It is most probably related to both boron implantation and RTA. Its concentration profile depth of 4 mm within the silicon substrate may be associated with defect complexes originating either from interstitials or vacancies. The profiles were used to distinguish between the two types of defect and to evaluate accurately their signature.