A Study on Distributions of Boron Ions Implanted by Using B and BF2Dual Implantations in Silicon

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For the fabrication of PMOS and integrated semiconductor devices, B, <TEX>$BF_2$</TEX> and dual elements with B and <TEX>$BF_2$</TEX> can be implanted in silicon. 15 keV B ions were implanted in silicon at <TEX>$7^{\circ}$</TEX> wafer tilt and a dose of <TEX>$3.0{\times}10^{16}\;cm^{-2}$</TEX>. 67 keV <TEX>$BF_2$</TEX> ions were implanted in silicon at <TEX>$7^{\circ}$</TEX> wafer tilt and a dose of <TEX>$3.0{\times}10^{15}\;cm^{-2}$</TEX>. For dual implantations, 67 keV <TEX>$BF_2$</TEX> and 15keV B were carried out with two implantations with dose of <TEX>$1.5{\times}10^{15}\;cm^{-2}$</TEX> instead of <TEX>$3.0{\times}10^{15}\;cm^{-2}$</TEX>, respectively. For the electrical activation, the implanted samples were annealed with rapid thermal annealing at <TEX>$1,050^{\circ}C$</TEX> for 30 seconds. The implanted profiles were characterized by using secondary ion mass spectrometry in order to measure profiles. The implanted and annealed results show that concentration profiles for the <TEX>${BF_2}^+$</TEX> implant are shallower than those for a single <TEX>$B^+$</TEX> and dual (<TEX>$B^+$</TEX> and <TEX>${BF_2}^+$</TEX>) implants in silicon. This effect was caused by the presence of fluorine which traps interstitial silicon and <TEX>${BF_2}^+$</TEX> implants have lower diffusion effect than a single and dual implantation cases. For the fabricated diodes, current-voltage (I-V) and capacitance-voltage (C-V) were also measured with HP curve tracer and C-V plotter. Electrical measurements showed that the dual implant had the best result in comparison with the other two cases for the turn on voltage characteristics.