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

Ion implantation of 1.5xl0¹⁶-cm⁻² H⁺ at 8 keV or 1.0xl0¹⁴-cm⁻² Ar⁺ at 70 keV was carried out at room temperature (RT) to crystalline silicon in advance of ion implantation of 1.0×10-15-cm⁻²B⁺ at RT. Decrease in the crystalline volume ratio and generation of crystalline defects were promoted by the first H⁺ or Ar⁺ implantation. Subsequently post heating at 300°C for 30 min decreased the sheet resistivity to 520 and 890 Ω/sq in the cases of the H⁺ and Ar⁺ implantation, respectively. The decreases in the sheet resistivity by 300°C post annealing is interpreted that formation of crystalline defects by the first H⁺ or Ar⁺ implantation decreased the activation energy for moving boron atoms from the interstitial to lattice sites and achieved carrier generation at the low temperature.