3-dimensional Analysis of Thin Surface Layers with SIMS

The central part of this project is the in-depth research of thin surface layers with Secondary Ion Mass Spectroscopy (SIMS). These thin layers on different materials play an important role in many technical tasks. The project`s aim is to analyse on one hand passivation layers that were formed naturally (e.g. due to corrosion) and on the other hand layers that are applied to materials with a considerable technical effort to achieve certain electrical, optical and/or mechanical surface effects. These examinations will lead to a better understanding of corrosion mechanisms in general and to increase qualities of technically applied layers. The materials to be examined in this project are all high performance materials. For the naturally formed surface layers the following examinations shall be performed: room temperature corrosion layers of pure molybdenum middle temperature corrosion (up to 500C) layers of molybdenum alloys high temperature corrosion layers of titanium-aluminium alloys at 1100C For the technically applied layers the following systems shall be examined: oxidic and nitridic abrasion-resistant coatings produced by TiAl reactive sputtering metallic sputter layers for the semiconductors industry. Because of its high detection strength (all elements can be detected within ppm range, even hydrogen) Secondary Ion Mass Spectroscopy (SIMS) is able to verify the influence of trace elements. Imaging SIMS can detect contaminations on surfaces with a lateral resolution of up to 0.2 m. Since this method is able to analyse three dimensional distributions of contaminations and dopands, the distribution depending effects can be determined as well. Another valuable advantage of SIMS is its isotope-selectivity. This feature can be used to examine which difflusion mechanisms are relevant for the growth of passivation layers on materials by using isotope enriched gases during the oxidation process. Therefore this project wants to make use of high temperature oxidation with 18O and 15N isotopes at up to 1100C. For the data evaluation part of the project works about the classification of SIMS distributions are planned in order to be able to recognise and determine different phases on surface layers (e.g. carbonitride on molybdenum) and 3- D depthprofiles. The use and adaptation of new 3D-image processing algorithms shall enable the evaluation of the large data volume of such measurements. A typical problem of any microscope measurement is the image degradation due to possible low signal-noise ratios and disturbing side-effects. This shall be handled by a combination of denoising and deconvolution algorithms in order to improve following image processing (e.g. classification). This project is a close co-operation with the Austrian Industry and two internationally acclaimed research groups: ISAS (Institute for Spectral Chemistry and Applied Spectroscopy, Dortmund) for additional SNMS measurements. ISPRA (Institute for Advanced Materials, Joint Research Centre of the European Commission, ISPRA, Italy) for high temperature oxidations.

The characteristics of thin layers do not only depend on the chemical composition of the layer, but also on the distribution of the elements contained in the layers. On the one hand inhomogeneous distribution or inclusion of contaminations may lead to a loss of quality; on the other hand in some applications trace elements may improve the behavior or lead to novel material properties and are thus added intentionally. Because of its high detection strength (all elements can be detected within ppm range, even hydrogen) Secondary Ion Mass Spectroscopy (SIMS) is a very good technique to verify the influence of trace elements. Imaging SIMS can detect contaminations on surfaces with a lateral resolution of 1m. Distribution effects and homogeneity of the layer can also be analyzed as SIMS can give 3 dimensional images of the sample. This project have dealt with the analysis of thin layers by SIMS during the last 3 years, thereby various thin layers, mainly nitridic and oxidic ones, were investigated. Additionally the SIMS measuring technique and data requisition could be improved substantially. Within this project 36 scientific articles were published and 3 PhD Thesis and 6 diploma works were finished. The oxidation behavior of thin layers is one limiting factor the industrial application, therefore one major field of research was oxidation layers and oxidation of layers. Furthermore tribological layers such as AlSn layers for bearings and TiN hard layers for cutting tools have been analyzed to get deeper understanding of their properties. Many layers are produced by sputtering of a sputter target, therefore the content and 3D distribution of trace elements in these targets is important. The results of this project indicate that a homogeneous distribution is necessary to optimize the layer qualities. These layers and implantations play a dominant role in the semiconductor production. Especially the effect of high energy implantation for defect generation was investigated. Using imaging techniques the data evaluation is one integral task. In this project several classification techniques were tested for application in the field of imaging analysis. New techniques of image fusion developed for medical applications were adapted for surface analytical tasks. Furthermore improvements of image corrections and visualization were realized.