High current ribbon beam ion implanter

Abstract

A compact high current broad beam ion implanter employs a high current density source, a bending magnet to steer the beam and straighten trajectories, and a multipole unit extending across the beam path to tailor a precise one-dimensional beam current distribution which yields a uniform implantation dose with a possibly non-uniform workpiece transport assembly. In one embodiment, the multipole unit is a separate magnet assembly positioned adjacent to a output face of the bending magnet, and includes one or more ranks of closely-spaced pole elements, controlled so the drive current or position of each pole element is varied to affect a narrow band of the beam passing over that element. In another embodiment, the bending magnet is an analyzing magnet which directs a desired species through a resolving slit, and a second magnet deflects the resultant beam while rendering it parallel and further correcting it along its width dimension. As with the first embodiment, multipole elements are adjusted to fit the derived profile. Both magnets preferably have relatively large pole gaps, wide input and output faces, and deflect through a small radius of curvature to produce a beam free of instabilities. The multipole elements are adjacent to or incorporated in the dipoles, preferably at a downstream side, and operate to shift beam power along the width dimension, locally adjusting the beam current density to achieve the desired profile. A separate multipole array, such as an electromagnet with blade poles oriented at progressive angles may adjust the entrance beam.