Electrical characterization of p+/ n shallow junctions obtained by boron implantation into preamorphized silicon

Abstract

Electrical characteristics of p +/ n diodes obtained by boron implantation into amorphous silicon layers formed by a prior implantation of Si + ions are presented. The absence of channeling phenomena (preamorphization), the low boron implantation energy (10–20 keV), and the post-implantation low temperature anneal (600–1000°C) or rapid anneal (electron beam) allow to obtain very shallow junctions (0.1–0.3 μm). Particular attention is given to analyse effects on the reverse diode current from dislocation loops which are formed at the amorphous-crystalline interface during annealing. If the dislocation loops are outside of the space charge region, the diodes show a low leakage current (∼ 1 nA/cm 2 at - 1 v), but the reverse current increases strongly when this residual damage falls into the depleted n-region. Experimental I–V characteristics are in excellent agreement with a numerical simulation, which takes into account a strong lifetime degration associated with the dislocation loops.