Ion implanter with plural surface potential sensors

摘要

An ion implanter including an ion beam generator for irradiating an ion beam toward a rotary drum having a front surface with a number of substrates fixed and equally spaced circumferentially thereof. The rotary drum is supported for rotation and reciprocation so that the substrates are exposed in succession to the ion beam. A plurality of surface potential sensors are positioned adjacent the front surface of the rotary drum. The surface potential sensors are positioned at different angular distances with respect to the ion beam for generating surface potential signals in response to surface potentials on the respective substrates. The surface potential sensors may be positioned on a line extending in a direction of reciprocation of the rotary disc for producing surface potential signals in response to surface potentials at different positions on each of the substrates.