Fracture of Submicron Thin Metal Films During Cyclic Loading

One current trend in microelectronics and MEMS is to develop micro devices based on plastic substrates. This allows for new applications, for instance, by integrating such flexible devices into the personal environment like textiles. Furthermore, the use of polymers offers a high potential for cost effective production for mass products. Depending on the application, devices on plastic substrates are fabricated by forming the polymer, and depositing and patterning one or several thin films onto the substrate. One reliability issue in such devices is the stretchability of the thin films during mechanical and/or thermal loading conditions. Under monotonic loading, however, it has been shown that cracking of metal films on compliant substrates only occurs, when large strains (>10%) are reached. In contrast, cyclic mechanical or thermal loading conditions with typical strain ranges between 0.1% and 1% lead to damage formation such as cracking, surface roughening and delamination [

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