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Depth resolution optimized sputter depth profiling of a polycrystalline Al layer

Depth profiling of thin films by inert gas sputtering is one of the most important applications of Auger electron spectroscopy and X-ray photoelectron spectroscopy. Such an analysis monitors the elemental in-depth composition of the thin film system and controls the quality of the manufacturing process. A challenging task of a sputter depth profile measurement is the determination of the interface contaminations. Interface contaminations are only detectable if the depth profile data were measured with a sufficient depth resolution. Interface contaminations are crucial, because they strongly influence the mechanical and electrical properties of the whole thin film system. The depth resolution of unidirectional sputter depth profiling for polycrystalline samples is limited by the sputter yield differences attributed to grains having different crystalline orientations relative to the incoming ion beam. Therefore depth resolution optimized sputter depth profiling of polycrystalline thin films requires dedicated experimental approaches. If the sample is rotated during ion sputtering the depth profile is recorded with a better depth resolution because the ion impact direction relative to the grains orientation varies. If depth profiling can be performed on a single grain only, the depth resolution is improved, too. These approaches are applied to the depth profiling and interface contamination analysis of a 5000 nm thick polycrystalline Al layer. An O contamination at the interface of the Al to the Si substrate was detected utilizing these high depth resolution depth profiling methods.