Ensemble RBS: Probing the compositional profile of 3D microscale structures

Abstract

Rutherford backscattering spectrometry (RBS) is an analytical method able to provide quantitatively elemental information with high accuracy in the near surface region of samples. However, the technique conventionally lacks the required (sub)micron spatial resolution for many semiconductor applications. Firstly, the ion beam current of a highly focused beam is very small, limiting the analytical sensitivity of the measurement. Secondly, the exposure of a sample to a highly focused ion beam readily leads to sample damage, surface sputtering, and accordingly to a measurement error. As a solution to these problems, ensemble RBS is presented whereby multiple devices are measured simultaneously using a broad beam. A judicious choice of the scattering conditions and related data interpretation nevertheless leads to the ability to analyse 3D-devices of micrometre sizes. We demonstrate the potential of this approach through the analysis of atomic species present on the different surfaces of 3D-microfluidic devices. The performance of the technique is demonstrated by the analysis of microfluidic devices after Pt deposition at an oblique angle, and the analysis of the same microfluidic devices after a site-selective deposition of a sub-monolayer of Hf. Further, the performance of ensemble RBS on these structures is compared to the one of microbeam RBS.