Quantitative analysis of thin film compositions using EFTEM combined with RBS and ERDA

Abstract

Analytical electron microscopy today is an emerging technique allowing for the composition analysis of solids with high spatial resolution down to 1 nm or less. In particular energy filtered transmission electron microscopy (EFTEM) is becoming a technique which is frequently applied to study nanometric semiconductor device features. Among the advantages of EFTEM are the possibility to directly correlate elemental distributions and structural or morphological details as well as the good sensitivity particularly for low Z elements. However, quantitative information on the local composition is difficult to be obtained from EFTEM. This is due to the lack of accurately known elemental ionization cross-sections for the experimental conditions used in a particular EFTEM experiment, in which the TEM parameters are usually chosen in an attempt to give optimum imaging conditions. In addition, theoretical predictions of such cross-sections are still too inaccurate today. In this paper it is shown that it is possible to overcome these difficulties by supplementing EFTEM with standardless ion beam analysis techniques such as Rutherford Backscattering Spectroscopy (RBS) and Elastic Recoil Detection Analysis (ERDA). By this, the high resolution of the microscopic technique is combined with the inherent accuracy of nuclear probe techniques and 2-d distributions of absolute atomic densities are obtained. This is examplified using multi-layer structures of Si–C–N dielectrics and multi-elemental carbon-rich spacer layers on silicon.