Characterization of multicusp-plasma ion source brightness using micron-scale apertures

The brightness of a multicusp-plasma ion source was characterized to determine its suitability for a proposed maskless ion-beam lithography system. In order to be competitive with similar systems utilizin- electron sources, the brightness requirement must be met to satisfy throughput demands. For this requirement, 1 nA into each beam diameter of 50 nm is needed at the target plane; this implies a brightness of about 1000 A/cm(2)/sr at the entrance to the objective lens. The brightness of the source has been characterized using 5-mum-diam extraction apertures under two different extraction configurations: (1) with the apertures directly illuminated by the source and (2) with the apertures flooded using an extraction system. The maximum brightness achieved for either configuration was 15 A/cm(2)/sr at 3 keV beam energy, He+ ions, and continuous wave operation. Although this configuration falls short of the requirement for high-throughput exposures, it is also possible to operate the multicusp-plasma ion source in pulsed mode. This would give higher current densities, which may also give adequate brightness as well. (C) 2001 American Vacuum Society.