A method and apparatus for making phase shift masks are provided wherein an anti-reflective coating used on an opaque pattern layer of the mask fully covers the opaque pattern layer and has not been etched in the etching process to form the phase shift mask. The diffuser comprises an inner horn and an outer horn positioned concentrically around the inner horn. In an embodiment, employing polished graphite electrostatic lens electrodes does not require the time-consuming conditioning operations under vacuum that are typically needed with conventional graphite electrodes, and thus offers the advantage of increased uptime for an ion implantation system.