Ion implanter with plural surface potential sensors

An ion implanter comprising:

• means for irradiating an ion beam;
• a rotary disc having a front surface with a number of substrates fixed and equally spaced circumferentially thereof, said rotary drum being supported for rotation and reciprocation so that said substrates are exposed in succession to the ion beam;
• a plurality of surface potential sensors positioned adjacent said front surface of said rotary disc, said surface potential sensors being respectively positioned at different positions on a line extending in a direction of reciprocation of said rotary disc for producing a plurality of respective surface potential signals in response to surface potentials at said different positions on each of said substrates;
• and
• means responsive to the respective surface potential signals for estimating a surface potential produced on each of said substrates at a time at which and at a position where each substrate is exposed to the ion beam.

An ion implanter, comprising:

• a rotary disc supported for rotation about an axis and reciprocation along a line and having a surface having a plurality of substrates fixed on said surface of said rotary disc at spaced intervals so that said substrates are positioned to be successively irradiated with an ion beam;
• means for selectively rotating and reciprocating said rotary disc;
• means for irradiating an ion beam to produce an ion beam spot at a predetermined position at said surface of said rotary disc so that said plurality of substrates are each irradiated with said ion beam at an irradiation target location;
• a plurality of surface potential sensors respectively positioned adjacent said surface of said rotary disc at predetermined locations relative to said irradiation target location to measure surface potential at a surface of each of said plurality of substrates after irradiation, each of said plurality of surface potential sensors respectively producing a surface potential signal representative of said surface potential on said substrate at said location of said surface potential sensor;
• and
• means responsive to the respective surface potential signals for estimating a surface potential produced on each of said angularly-spaced substrates when said each substrate is exposed to the ion beam.