Dose cup assembly for an ion implanter

An ion implanter comprising:

• an ion source to generate an ion beam;
• a platen to support a workpiece that is treated with the ion beam, the platen positioned within a process chamber of the ion implanter;
• a dose cup assembly comprising:
• a faceplate attached to a back wall of the process chamber of the ion implanter, the faceplate defining an opening;
• an aperture plate defining a plurality of slots;
• and
• a tunnel having walls and sidewalls and having a proximal end and a distal end, located between the faceplate and the aperture plate, such that the proximal end is nearer to the faceplate and the distal end is nearer to the aperture plate;
• and
• one or more current sensors disposed behind the plurality of slots in the aperture plate, wherein the ion beam passes through the plurality of slots to the one or more current sensors;
• wherein at least one of the faceplate, the walls, the sidewalls or the aperture plate has one or more exposed outer surfaces that comprise silicon.