Selective interface toughness measurements of layered thin films

Abstract

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.

Cyclic Deformation of Microcantilevers Using In-Situ Micromanipulation

“…In response to these needs, recent developments in the areas of microscale mechanical testing equipment and focused ion beam (FIB) milling technology has made it possible to perform mechanical testing on microscale features [2,3]. Specimen geometries such as microcantilevers [4,5] and micropillars [6] have been tested in various studies using in-situ or ex-situ nanoindenters to evaluate mechanical properties of single grains [4,[7][8][9][10], grain boundaries [11][12][13][14][15], thin films [16][17][18][19][20], etc. Most of the studies have been focused on monotonic loading, and very few on cyclic loading since it is more complex.…”

New Insights into Nanoindentation-Based Adhesion Testing

“…Some use indentation, 17,18 whereas others use complex micro-mechanical bending geometries and perform the experiments in situ with picoindenters in the scanning electron microscope (SEM) or transmission electron microscope (TEM). 19,20 In the flexible electronics area (films on compliant polymer substrates), tensile-induced delamination is prominent. 21,22 Nanoindentation, focused ion beam (FIB) milling, and confocal laser scanning microscopy (CLSM) are bringing more insight to adhesion testing as well as increasing the imaging areas compared with other available methods (atomic force microscopy (AFM) or profilometry).…”