Ion implantation apparatus

An ion implantation apparatus including a scanning unit, the scanning unit including:

• a scanning electrode device that allows a deflecting electric field to act on an ion beam incident along a reference trajectory and scans the ion beam in a horizontal direction perpendicular to the reference trajectory;
• and
• an upstream electrode device configured by a plurality of electrode bodies provided upstream of the scanning electrode device,
• wherein the upstream electrode device includes a first upstream reference voltage electrode disposed just upstream of the scanning electrode device and having an opening through which an ion beam passes,
• the first upstream reference voltage electrode includes
• a downstream surface that faces the scanning electrode device and is perpendicular to the reference trajectory, and
• a pair of aberration correctors provided in the downstream surface such that the opening is interposed therebetween in a vertical direction perpendicular to the horizontal direction and has a shape protruding toward or recessed from the scanning electrode device on the downstream surface, and
• wherein the opening has a thickness in a direction along the reference trajectory such that the thickness in a central portion disposed in the vicinity of the reference trajectory is different from the thickness of a circumjacent portion located away from the central portion in the horizontal direction by providing the pair of aberration correctors.