Depth scale calibration during sputter removal of multilayer systems by SNMS

Summary A key problem in sputter depth profile analysis is the conversion of bombardment time of primary ion dose into eroded depth. In particular during sputter removal of multilayer structures, both the total sputtering yieldY _tot and the particle density of the sample and, hence, the sputter erosion rate will in general vary between the different individual layers.The important role of this effect is demonstrated for Secondary Neutral Mass Spectrometry (SNMS) depth profile analysis of a model Ta-Si multilayer system where the observed ratio between individual Si- and Ta-layer removal times indicates an average film composition which is far off the TaSi₂-stoichiometry claimed by the manufacturer. The determination of absoluteY _tot as a function of sputter time from the recorded SNMS depth profile itself enables a non-linear calibration of the depth scale which yields a ratio ofd _Si/d _Ta = 2 between the individual Si and Ta layer thicknesses and, hence, confirms the true film stoichiometry.

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Kalibrierung der Tiefenskala beim Sputterabtrag von Vielschichtsystemen durch SNMS