Examining the influence of W thickness on the Si-on-W Interface: A comparative metrology analysis.

[Display omitted] • The Si-on-W interface between the two thin-films was measured by LEIS, XRR, and TEM. • Comparison of the characterization techniques is made possible by a standard quantification approach. • The sensitivity of LEIS and XRR measurements of thin-film interfaces is investigated. • The sub-atomic effect of the thickness of the W film on the Si-on-W interface is quantified. • A structure with 20 nm W has a sharper Si-on-W interface than a structure with 4 nm W. W/Si thin-film multilayer structures are used in various applications such as X-ray, neutron, and extreme ultraviolet optics. The interfaces between the films play such a fundamental role in the performance of these structures that a sub-nanometer and non-destructive characterization of such interfaces is necessary, albeit challenging. In this study, we investigate the interface Si-on-W and the effect of W thickness on such an interface using low energy ion scattering (LEIS), X-ray reflectivity (XRR), and transmission electron microscopy (TEM). We extract the Si-to-W error-function-like compositional change to quantitatively compare the effective interface width measured by the different techniques. We demonstrate that, in the case of Si-on-W, the effective interface width measured by LEIS and XRR agrees with the values extracted from TEM analysis within a 0.1 nm error margin. Noting that TEM is a destructive method, these results exemplify the value of LEIS and XRR as analysis techniques for resolving thin film interfaces. Surprisingly, all techniques employed in the study show that a structure with 20 nm of W has a sharper Si-on-W interface compared to a structure with 4 nm of W, which we interpret as the effect of both the correlated roughness from the substrate − present in the case of 4 nm W − and the larger crystals − present in the W film in the case of 20 nm W- resulting in less intermixing. This directly shows the value of extracting exact interface widths for the analysis and understanding of thin film growth in multilayer systems. [ABSTRACT FROM AUTHOR]