Design of a high resolution focused ion beam system using liquid metal ion source

We have made a Monte Carlo simulation to design a high resolution ion beam column with a liquid metal ion source (LMIS), which employs Koehler illumination. The use of Koehler illumination is one of the few ways to avoid the problem caused by the non-Gaussian current density profile, which is due to the stochastic angular broadening of the ion beam near the source. Thus we can predict a 20 nm beam spot size with 1 nm edge sharpness and about 1 pA of ion current on the target plane at 100 keV beam energy with a Ga LMIS.