An ion implanter system has a movable wafer support for holding a semiconductor wafer and a beam source that generates a beam for implanting ions in the semiconductor wafer while the wafer is moving. A plurality of path segments are identified, through which the wafer support is to move to expose the semiconductor wafer to the ion beam. A first position and a second position are identified for each respective one of the plurality of path segments, such that, when the wafer is in each first position and each second position, a perimeter of the beam projected in a plane of the wafer is tangent to a perimeter of the wafer. The ion implanter is configured to automatically move the wafer along each of the plurality of path segments, starting at the respective first position on each respective path segment and stopping at the respective second position on the same segment, so as to expose the wafer to the beam for implanting ions in the wafer.