Selective interface toughness measurements of layered thin films

Driven by the ongoing miniaturization and increasing integration in microelectronics devices, very thin metallic films became ever more important in recent years. Accordingly also the capability of determining specific physical and mechanical properties of such arrangements gained increasing importance. Miniaturized testing methods to evaluate, for example, the mechanical properties of thin metallic multilayers are therefore indispensable. A novel in-situ micromechanical approach is examined in the current study and compared to existing methods regarding their capability to determine the interface toughness of specific interfaces in multilayer configurations. Namely, sputter deposited copper and tungsten thin films with a thickness of approx. 500 nm on a stress-free silicon (100) substrate are investigated. The multilayer stacks consist of different materials that vary in microstructure, elastic properties and residual stress state. We examine the interface toughness via double cantilever beam tests, nanoindentation and novel miniaturized shear tests. The choice of a proper test method is indispensable when addressing strong interfaces, such as the W-Cu interface, in the presence of weaker ones. Finally, it is demonstrated that miniaturized shear testing is a very promising approach to test such strong interfaces as the interface of interest to fail is predefined by the sample geometry

Prospects of using small scale testing to examine different deformation mechanisms in nanoscale single crystals - A case study in Mg

The advent of miniaturised testing techniques led to excessive studies on size effects in ma-terials. Concomitantly, these techniques also offer the capability to thoroughly examine deformation mechanisms operative in small volumes, in particular when performed in-situ in electron micro-scopes. This opens the feasibility of a comprehensive assessment of plasticity by spatially arranging samples specifically with respect to the crystal unit cell of interest. In the present manuscript, we will showcase this less commonly utilised aspect of small-scale testing on the case of the hexagonal metal Mg, where, besides dislocation slip on different slip planes, twinning also exists as a possible deformation mechanism. While it is close to impossible to examine individual deformation mechanisms in macroscale tests, where local multiaxial stress states in polycrystalline structures will always favour multiple mechanisms of plasticity, we demonstrate that miniaturised uniaxial experiments conducted in-situ in the scanning electron microscope are ideally suited for a detailed assessment of specific processes. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Selective interface toughness measurements of layered thin films

Driven by the ongoing miniaturization and increasing integration in microelectronics devices, very thin metallic films became ever more important in recent years. Accordingly also the capability of determining specific physical and mechanical properties of such arrangements gained increasing importance. Miniaturized testing methods to evaluate, for example, the mechanical properties of thin metallic multilayers are therefore indispensable. A novel in-situ micromechanical approach is examined in the current study and compared to existing methods regarding their capability to determine the interface toughness of specific interfaces in multilayer configurations. Namely, sputter deposited copper and tungsten thin films with a thickness of approx. 500 nm on a stress-free silicon (100) substrate are investigated. The multilayer stacks consist of different materials that vary in microstructure, elastic properties and residual stress state. We examine the interface toughness via double cantilever beam tests, nanoindentation and novel miniaturized shear tests. The choice of a proper test method is indispensable when addressing strong interfaces, such as the W-Cu interface, in the presence of weaker ones. Finally, it is demonstrated that miniaturized shear testing is a very promising approach to test such strong interfaces as the interface of interest to fail is predefined by the sample geometry