WEAKENING FOCUSING EFFECT OF ACCELERATION-DECELERATION COLUMN OF ION IMPLANTER

摘要

A method and apparatus for weakening a strong focus effect of an acceleration-deceleration column (240) of an ion implanter during a deceleration mode are disclosed. The apparatus includes a tube lens (250) surrounding the ion beam (104) adjacent to a deceleration lens (260) of the acceleration-deceleration column (240). The tube lens causes a defocusing of the ion beam (104) at the entrance of the tube lens (250), which reduces the ion dispersion problem generated by the column. The invention also includes an accel-decel column and ion implanter incorporating the tube lens. An additional deceleration-suppression electrode (270) may also be added subsequent to the tube lens (250) for confining electrons within the tube lens.