Towards Unconventional Applications of Wire Bonding

Abstract: This thesis presents novel heterogeneous integration approaches of wire materials to fabricated and package MEMS devices by exploring unconventional applications of wire bonding technology. Wire bonding, traditionally endemic in the realm of device packaging to establish electrical die-to-package interconnections, is an attractive back-end technology, offering promising features, such as high throughput, flexibility and placement accuracy. Exploiting the advantages of state-of-the-art wire bonding technology and substitute the conventional micro welding approach with an innovative attachment concept, a generic integration platform for a multitude of wire materials is provided. This facilitates a cost-efficient and selective integration, which involves the attachment and shaping of a variety of intrinsically non-bondable wire materials. Furthermore, the selective integration of wire materials provides a simple method to generate complex suspended geometries, which circumvents the need for subsequent processing. The first part of this thesis reports of the integration of non-bondable shape memory alloy wires on wafer-level, which has led to an innovative method to fabricate micro actuators. Moreover, the integration of high performance resistive heating wires on chip-level is utilized to fabricate filament based infrared emitters, targeting non-dispersive infrared gas sensing of alcohol for automotive applications. In the second part, a series of unconventional applications of wire integration using the traditional thermo-sonic wire bonding approach is presented. A novel and low-cost nitric oxide gas sensor is realized by producing vertical bond wires featuring high aspect ratio. Next, the high placement accuracy of wire bonding tools is leveraged to integrate conductive metals cores for fabricating high aspect ratio through silicon vias. Finally, an advanced packaging approach for stress-sensitive MEMS gyroscopes is evaluated, which exclusively utilizes bond wires for realizing the die attachment.