Characteristics of ion beams from a Penning source for focused ion beam applications

Abstract

Focused ion beam characteristics, measured by using PMMA resist exposures, show significant improvement of the previously reported results for hydrogen ion beams. A beam current density of >50 mA cm−2 at 6–7 keV has been obtained over a spot size of 2.3 μm, estimated from the full width at half maximum of the intensity distribution. A single Einzel lens with magnification of about 0.1 was used. A target current density of >1 A/cm2 can be achieved with this beam for a lens system with overall magnification of ∼0.01. In experiments with Ar, both the discharge current and extracted beam current increased by more than a factor of 2 when the discharge cell length was increased by about 25% with respect to the nominal cell length for operation with H. Ar ion beams were extracted with an angular beam intensity of >5 mA sr−1, brightness (90% beam) of ∼103 A sr−1 cm−2 at 10 keV, and energy spread of ∼4.5 eV. Greatly improved beam characteristics, with brightness >104 A sr−1 cm−2, are expected by optimization of the source for Ar beams.