3D analysis of solids using sputtered MCs+ ions

The 3-dimensional characterization of solids by means of secondary-ion mass spectrometry is investigated. Monitoring MCs⁺ molecular ions emitted from surfaces upon Cs⁺ bombardment, laterally-resolved ion images were recorded with acquisition times of typically a few seconds which exhibit a dynamic sensitivity range in excess of 10² and a lateral resolution of about 2–3 μm. A quantitative data evaluation via relative sensitivity factors (RSFs) transforms them into elemental distribution maps. From the applied RSFs, local (i.e. erosion-time dependent) sputtering yields can be derived; together with atomic densities (which might be interpolated from pure-element values) a local depth scale (relative to some reference level) is assigned to each pixel of the 3D data volume recorded during the analysis. In conjunction with the elemental concentration values, this provides the possibility of a complete reconstruction of the 3D sample volume removed by sputtering. This approach is exemplified by means of a laterally inhomogeneous semiconductor test specimen.