Metals contamination reduction on the NV-8200P

Metal contamination was measured using O-leak SIMS and TXRF for surface contamination and dynamic SIMS for energetic contamination resulting from implantation of 80 and 250 keV arsenic at doses of 5×10¹⁵ atoms/cm². Aluminum sputtered from the wafer clamp and other parts in the endstation was the primary addition to the surface of the wafer, amounting to about 1.2×10 ¹³ atoms/cm². Energetic aluminum was found to increase with increasing ion energy to a level of about 5×10¹² atoms/cm² at 250 keV. Parts of the endstation and beam line which could be struck by ions in the beam were replaced with parts made of graphite or coated with plasma sprayed silicon. These changes resulted in the reduction of surface aluminum to about 5×10¹¹ atoms/cm² and energetic aluminum to about 3×10¹⁰ atoms/cm². Contamination of heavier elements is reduced to less than 5×10¹⁰ atoms/cm². These sources of contaminant species and modifications required to reduce them will be discussed