Abstract
With modern materials applications continually decreasing in size, e.g., microelectronics, sensors, actuators, and medical implants, quantifying materials parameters becomes increasingly challenging. Specifically, addressing individual constituents of a system, such as interfaces or buried layers in a multilayer structure, emerges as a topic of great importance. We demonstrate herein a technique to assess fracture parameters of different interfaces of a Cu-WTi-SiOx-Si model system based on in situ microcantilever testing in a scanning electron microscope. Positioning the initial notch position with respect to the interface of interest enabled selection of different crack paths, while an additional overlaid sinusoidal signal permitted continuous measurement of stiffness changes and thereby experimental measurement of the actual crack extension. We thus achieved continuous J–Δa curve measurements for the interface between Cu and WTi, the bulk WTi, and the interface between WTi and SiOx. The localized nature of this novel approach makes it generally applicable to testing specific interfaces.
Highlights
Due to the continuous drive towards more powerful devices, a wide variety of modern materials applications rely on very small structural features
The error estimation for L, L¢, B, and W are based on a measuring error of ± 5 pixels (± 40 nm), while the error estimation for the initial crack length a0 is based on the standard deviation of 20 individual measurements conducted on the fracture surface after the experiment
Once contact is established during elastic loading of the beam, the overall cantilever compliance overtakes the contribution from the contact compliance, as is evident from the constant compliance level observed before the occurrence of plastic deformation or crack extension
Summary
Due to the continuous drive towards more powerful devices, a wide variety of modern materials applications rely on very small structural features Depending on their application based on structural, semiconducting, or optical properties, this trend leads to an increasing number of different constituents confined to a very limited volume, such as multilayers or coatings of only a few tens to hundreds of nanometers in size. Due to the brittle nature of these materials, both groups were successfully able to apply linear elastic fracture mechanics concepts for the evaluation.[7] Given that some components in applied systems can exhibit rather pronounced ductility, e.g., heat sinks or conductive layers (Cu, Al), those approaches are insufficient and it appears necessary to advance the field towards miniaturized elastic–plastic fracture mechanics concepts for interface testing. This will enable a better understanding of interface-controlled fracture processes for a wider group of materials
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