An ion implantation system including an ion source for use in creating an ion beam is disclosed. The ion source has an ion source arc chamber housing that confines a high density concentration of ions within the chamber housing. An extraction member defining an appropriately configured extraction aperture allows ions to exit the source arc chamber. In a preferred embodiment, the extraction member defines a tailored extraction aperture shape for modifying an ion beam profile and producing a substantially uniform beam current across a dimension of the ion beam. The extraction aperture member defines an aperture in the form of an elongated slit having a width that varies, with wide ends and a narrow middle. The midsection of the extraction aperture has a narrower width than the opposite end sections. The tailored shape of the extraction aperture includes a central portion having a first width dimension, and first and second distal portions extending from opposite sides of the central portion, the opposed distal portions having a second width dimension that is greater than the first width dimension of the central portion.