COMPARISON OF DEPTH RESOLUTION FOR DIRECT-CURRENT AND RADIOFREQUENCY MODES IN GLOW-DISCHARGE OPTICAL-EMISSION SPECTROMETRY

The correlation between depth resolution and the crater formation process was investigated for depth profiling in two glow discharge modes, viz,, direct current (de) and radiofrequency (rf) glow discharge optical emission spectrometry, The rf system described functions without a matching unit and shows a very high reproducibility and stability (within several tens of milliseconds), which are comparable to those obtained in the de mode, By using conductive samples with a well known multilayer structure (five double layers with 100 nm Cu and 100 nm CrNi each), the discharge parameters for maximum depth resolution were determined and crater formation during the sputtering process was investigated, The best depth resolution was found at the same values of pressure and power for both modes, Under these optimized conditions the depth resolution increases linearly with the sputtered depth and amounts to 5-10% of the latter, Finally, the CRAS model was applied to simulate an intensity-time profile in order to discuss the depth resolution achieved.