Metals-contamination-reduction program for the Varian EHP-220/500 medium-current ion implanter

The results of a program to minimize metals contamination for the Varian EHP-220/500 medium-current ion implanter are presented. Additional graphite and Si-coated shields were added to the beamline and metal contamination associated with 80-kV As+ implants was measured by SIMS. Total contamination (surface + energetic) was reduced to as low as 28 ppm for Al, 3 ppm for Fe and 2 ppm for Cr. Energetic components of the contamination are consistent with models of knock-on distributions from an 80 kV As+ implant.