Interfacial effects during the analysis of multilayer metal coatings by radio-frequency glow discharge optical emission spectroscopy : Part 1. Crater shape and sputtering rate effects

Abstract

In depth profile analysis by radio-frequency glow discharge optical emission spectroscopy (rf-GDOES) techniques, the depth resolution mainly depends on the roughening induced during the sputtering and the resulting crater geometry. In this work we have tried to isolate the contributions of the different effects that degrade the depth resolution in GDOES analysis of metal coatings deposited on silicon substrates. First, the existence of an edge well around the crater (“edge effect”), deeper than the crater bottom, results in an initial rise of the quantified profile of the bottom layer before reaching the interface. A second effect is the induced roughening of the crater bottom, which produces a broadening of the interface width. Finally, we have explained the long tails observed after crossing the interface in the metal profiles in terms of the sputtering of material re-deposited at the crater wall. The importance of these effects was tested for the particular case of multilayer stacks consisting of alternating chromium and titanium layers of different thicknesses. Reversing the order of the layers showed the influence of different sputtering rates of the materials in the depth profile. The profiles of materials with high sputtering rate (i.e., chromium in this study) become less affected than material with low sputtering rate (titanium) due to lower mixing of the layers.