The application of liquid metal ion sources to ion-microprobe secondary ion mass spectroscopy

Abstract

Secondary ion mass spectroscopy microprobe analysis is readily achieved by application of the liquid metal field ion source for formation of low energy (⩽ 10 keV) sub-micron ion probes. Various metals are suitable for operating these sources including gallium and caesium. The gallium source is fully compatible with U.H.V. techniques and is easily fitted to multitechnique surface analysis instruments. A gallium microprobe, the “MIG100”, has been in operation on a demonstration dedicated SIMS instrument, “SIMSLAB”, for more than one year, and has proven very reliable and easy to operate. A wide variety of samples have been studied with this probe including superconductors, steels, alloy fractures, optical fibres, integrated circuits, catalysts, polymers and biological specimens. Further developments have been made and now results from a caesium probe, “CIG200”, and a 30-keV gallium probe, “MIG300”, have been obtained. The caesium probe provides not only the microprobe capability but also enhances the sensitivity for many electronegative species such as the common dopants P, Se, and As used in semiconductor technology. The “MIG300” extends the image resolution capability of the gallium probe on a new SIMS instrument which also incorporates a duoplasmatron ion probe for ultimate sensitivity and depth profiling performance.