Influence of substrate-boron concentration on the residual end-of-range defects in 450 °C annealed As+-implanted junctions

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Abstract
In order to clarify the origin of enhanced leakage currents observed in As+‐implanted junctions annealed at a temperature as low as 450 °C [M. M. Oka, A. Nakada, K. Tomita, T. Shibata, T. Ohmi, and T. Nitta, Jpn. J. Appl. Phys. 34, 796 (1995)], two‐step implantation/anneal experiments have been conducted and the spatial distribution of end‐of‐range defects has been investigated. As a result, it has been demonstrated that the residual damage in 450 °C annealed junctions is strongly influenced by the doping level of p‐type silicon substrate. The defects were found deeply distributing in the substrate, i.e., about 350 nm below the silicon surface when the doping level was 2.5×1015 cm−3. The defect distribution further extends for higher boron doping levels. Taking these experimental results into account, As +‐implanted n+p junctions were formed on substrates having varying doping levels. About two orders of magnitude reduction in the leakage current was observed with decrease in the substrate boron concentration from 1016 to 1014 cm −3. For low boron concentration of 1.6×1014 cm−3, the leakage current level as low as 1.7×10−9 A/cm2 has been achieved by a 450 °C postimplantation annealing.