Ion beam contamination during P+ source/drain ion implantation

This paper describes the studies performed to determine whether or not a high energy boron contaminant was being introduced during a BF₂, P⁺ source/drain implant and its impact on critical electrical device parameters and sort yields. The study confirmed the presence of a high energy boron contaminant during P⁺ implant on a medium current ion implanter. The contaminant significantly altered both PMOSFET threshold voltage and sort yield. While control of source vacuum during P⁺ implant impacted the degree of contaminant present, it could not be effectively eliminated. A manufacturable solution could only be achieved by introducing a beam filter and controlling source vacuum to effectively eliminate the high energy boron contaminant. Modification of the P⁺ implant conditions to eliminate the high energy contaminant significantly improved DC parametric and wafer sort yields