Ion etching methods for depth profiling of complex three-dimensional samples in combination with scanning Auger electron microscopy

Abstract

Ion etching of surfaces combined with detection of secondary events (particles or radiation emitted) are used for depth profiling of samples with interesting features at-, near-, or somewhat below the surface. These methods are destructive and relatively slow, and compete with non-destructive methods like Rutherford backscattering spectroscopy, energy-dispersive X-ray spectroscopy in the scanning electron microscope or angle-resolved photoemission spectroscopy, which are non-destructive and relatively faster methods. In this work we have concentrated on the use of noble gas ion sputtering with low-energy beams in combination with electron excited Auger electron spectroscopy and imaging for analysis of nanostructured and microstructured samples. No attempt will be made here to justify this method over the other methods, as their relative merits depend on the nature of the sample and the problem at hand. We have thus chosen to study samples and problems for which this technique would be obvious to use. This work is also aimed at providing practical standards and guidelines (“metrology”) for the use of the technique in the context of industrial nanotechnology. The use of Auger electron spectroscopy instead of photoemission spectroscopy is preferred for laterally non-uniform samples due to the presently better resolution capabilities of electron beams and narrower information depths of typical Auger electron transitions. The use of Auger electrons for concentration sampling, and low-energy beams of noble gas ions for sputtering, reduces the adverse influence of atomic mixing. In this report two systems are intensively studied with sputter profiling in combination with Auger electron spectroscopy and scanning electron imaging: a hard disk and a surface of a stainless-steel sample.