Ion sources for large area processing (invited)

Abstract

Large area ion sources have been used in ion doping systems in the field of LCD production. In these ion sources good uniformity and wide dynamic range in beam current are both required to achieve the good dose uniformity in wide dose range. A new ion source which uses dc arc discharge with three filaments, each of which is controlled individually, is now in the production lines instead of the conventional rf discharge type. Better than 5% of beam uniformity across 600 mm is achieved by an automated feedback control using beam profile data taken by a built-in beam profiler in less than 10 s from arc ignition. Another emerging requirement is high beam purity, for the ion beams from these ion sources are used without mass analysis. The hydrogen ion fraction was successfully reduced by magnetically retarding the hydrogen ions to less than 5%. A large area ion source having a newly designed mass separating structure is developed. The structure is comprised of a permanent magnet array and a beamlet scanner just after the multiple-slot beam extraction electrode system. All the unwanted ion species in the beam can be eliminated to a good level.