H− beam based projection microlithography: A conceptual study of the beam parametersa

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 ∼1–5 A/cm2 and a normalized brightness of ∼7×1012 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.