Dual ion implantation of non-dopant and dopant ions into Si for defect engineering of shallow p+-junctions

Dual ion implantation of F had B into silicon is studied. In a pre-amorphized silicon layer by F⁺ implants prior to B⁺ implantation at 10 keV with 3×10¹⁵/cm², broadening of B profile can be suppressed markedly in as-implanted B profiles. For instance, the depth of 0.23 μm at a B concentration of 1×10¹⁸/cm³ decreases to 0.18 μm by this pre-amorphization. When these layers are annealed at 950°C, B atoms diffuse rapidly 2.3 times faster in the pre-amorphized layer than in the single B⁺ implantation. In the high dose F⁺ implantation at doses above 1×10¹⁵/cm², F is trapped with annealing at the peak of the B profile as well as at the F profile peak and near the amorphous-crystalline interface. The effects of F dose and annealing temperature on the F precipitation are described