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

Dual ion implantation of F had B into silicon is studied. In a pre-amorphized silicon layer by F/sup +/ implants prior to B/sup +/ implantation at 10 keV with 3/spl times/10/sup 15//cm/sup 2/, broadening of B profile can be suppressed markedly in as-implanted B profiles. For instance, the depth of 0.23 /spl mu/m at a B concentration of 1/spl times/10/sup 18//cm/sup 3/ decreases to 0.18 /spl mu/m by this pre-amorphization. When these layers are annealed at 950/spl deg/C, B atoms diffuse rapidly 2.3 times faster in the pre-amorphized layer than in the single B/sup +/ implantation. In the high dose F/sup +/ implantation at doses above 1/spl times/10/sup 15//cm/sup 2/, 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.