H- BEAM BASED PROJECTION MICROLITHOGRAPHY - A CONCEPTUAL STUDY OF THE BEAM PARAMETERS

The current trends of research and development work in ion-beam microlithography are examined with particular emphasis on the choice of ion sources and the beam parameters. The common approach with duoplasmatron-type ion sources for projection ion-beam lithography is revisited, and the suitability of H- beams is examined. The beam brightness and energy spread, which constitute the figure of merit of a beam, appear to be better in the case of H- beams. From a surface plasma source type discharge operating under stable condition, H- beams with an emission current density of approximately 1-5 A/cm2 and a normalized brightness of approximately 7 x 10(12) A/(m rad)2 can be extracted. Several key issues of an ion-projection lithography device, such as the ion source parameters, beam optics, and thermal load are discussed.