Two-Step Ion Implantation used for Activating Boron Atoms in Silicon at 300°C

The H+ or Ar+ precursor implantation at room temperature (RT) was proposed to activate boron atoms subsequently implanted in single crystalline silicon by post heating at a low temperature. The two-step ion implantation of 1.5×1016 cm−2 H+ at 8 keV followed by 1.0×1015 cm−2 B+ at 40 keV for both surfaces of silicon and 1.0×1014 cm−2 Ar+ at 70 keV followed by 1.0×1015 cm−2 B+ at 40 keV resulted in low sheet resistivities of 520 and 890 Ω/sq, respectively by post heating at 300°C for 30 min. Their activation ratios were estimated as 22 and 13%. The optimization of the projected ranges of 79 nm for 6×1013 cm−2 Ar+ at 70 keV and of 46 nm for B+ at 10 keV further decreased the sheet resistivity to 392 Ω/sq and increased the activation ratio to 29.5%. The activation of B+ implanted region at 300°C probably resulted from a decrease in the activation energy induced by a decrease in the silicon bonding energy promoted by the first H+ or Ar+ precursor implantation.