SIMS using gas field ion sources to approach ultimate spatial resolution

Continuously shrinking object dimensions lead to an enhanced demand on spatial resolution and surface sensitivity of modern analysis techniques. Secondary Ion Mass Spectrometry (SIMS), as one of the most powerful technique for surface analysis, performed on nanometer scale may comply with this challenge. The mass of sputtered ions directly serves elemental and molecular information and even allows measuring isotope concentrations.

During last decades, primary ion species used in SIMS have optimized in terms of best ionization probabilities and small molecule fragmentation. Thereby, highest mass-resolution has been one of the biggest design goals in the development of new SIMS spectrometers. In contrast to former developments, our approach aims for ultimate spatial resolution.

Typically the lateral resolution is limited by the probe size of the primary ion beam. Minimal probe sizes below 1 nm can be achieved using Gas Field Ionization Sources (GFIS) in a Helium Ion Microscope (HIM). Recently, SIMS has been achieved by implementing Time-of-Flight (TOF) spectrometry to the HIM [1, 2] as well by adding of a sophisticated magnetic sector field analyzer [3]. In this way SIMS could be performed with unprecedented spot sizes.

We will discuss constrains, limits, benefits and drawbacks of the approach. The technical realization will be shown as well as first results and derived conclusions for the practical use of this promising technique.