Comparison of depth profiling techniques using ion sputtering from the practical point of view

Abstract

The depth profiling methods: Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), glow-discharge optical emission spectroscopy (GDOES), and secondary ion mass spectrometry (SIMS) are compared in respect to the investigation of thin films with thickness in the nm-range. All these methods are using ion sputtering for sample erosion. The focus of this work is concentrated on measuring procedures, which routinely can be used in surface analytical laboratories. However, particular interest concerns to the optimization of both experimental conditions and data interpretation. A series of NiCr(Si)/CrSi multi-layer samples with single layer thickness from 5 to 50 nm has been investigated. The results show that all the methods are principally suited for nm-analysis. The most reliable results are obtained by AES and XPS, which lead to additional chemical information useful for quantification. GDOES is characterized by very fast measurement and easy data interpretation, however, mainly crater shape effects lead to a poor concentration quantification of these thin films. SIMS is advantageous for impurity investigation in those thin films, too. The depth calibration of the thin film regions was generally insufficient. In our opinion, the high number of interfaces prevent steady state sputter conditions. Here, additional transmission electron microscopy investigations are necessary to elucidate the exact single layer thickness.