INFLUENCE OF SUBSTRATE-BORON CONCENTRATION ON THE RESIDUAL END-OF-RANGE DEFECTS IN 450 DEGREES-C ANNEALED AS-IMPLANTED JUNCTIONS()

In order to clarify the origin of enhanced leakage currents observed i n As+-implanted junctions annealed at a temperature as low as 450 degr ees C [M. M. Oka, A. Nakada, K. Tomita, T. Shibata, T. Ohmi, and T. Ni tta, Jpn. J. Appl. Phys, 34, 796 (1995)], two-step implantation/anneal experiments have been conducted and the spatial distribution of end-o f-range defects has been investigated. As a result, it has been demons trated that the residual damage in 450 degrees 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., abo ut 350 run below the silicon surface when the doping level was 2.5 X 1 0(15) cm(-3). The defect distribution further extends for higher boron doping levels. Taking these experimental results into account, As+-im planted n(+)p junctions were formed on substrates having varying dopin g levels. About two orders of magnitude reduction in the leakage curre nt was observed with decrease in the substrate boron concentration fro m 10(16) to 10(14) cm(-3). For low boron concentration of 1.6 X 10(14) cm(-3), the leakage current level as low as 1.7 X 10(-9) A/cm(2) has been achieved by a 450 degrees C postimplantation annealing. (C) 1996 American Institute of Physics.