Development of A Low-Temperature Hermetic Packaging Technology for Vibrating MEMS Devices

Date

2024-9

Author

Balcı, Leman Dicle

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MEMS, or micro-machining technology, has enabled the miniaturization of integrated systems with mechanical components, finding applications in various industries, including medical implants. In biomedical applications, MEMS-based sensors have become promising solutions for fully implantable cochlear implants (FICI). Lead zirconate titanate (PZT)-based piezoelectric transducers and harvesters, due to their ability to generate the required power levels to stimulate hearing neurons, are ideal for FICI systems. However, the fragile mechanical structures of these devices necessitate a specialized packaging method to protect them from environmental conditions. Additionally, low-temperature encapsulation is crucial for preserving the piezoelectric properties of PZT material by avoiding Curie temperature and preventing depolarization. This thesis presents the development of a low-temperature, hermetic packaging technology for vibrating MEMS devices, specifically targeting piezoelectric acoustic transducers used in FICI systems. A significant challenge in adapting the Au-In TLP system to MEMS technology is the rapid formation of intermetallic compounds during the bonding process. This research addresses this issue by optimizing the Au-In TLP bonding recipe, resulting in a void-free, robust packaging solution with an impressive shear strength of 91.3 MPa and fully hermetic seal. The developed hermetic packaging technology incorporates two silicon caps with Au-In TLP bonding method to hermetically seal the sensor, providing an isolated environment inside the package and allows mechanical structures to vibrate freely without damage. To minimize the footprint and achieve electrical connection to the macroworld, a lateral feedthrough design is utilized.

Subject Keywords

Hermetic packaging, Piezoelectric acoustic transducer, Transient liquid-phase bonding, Au-ın TLP systems

URI

https://hdl.handle.net/11511/111499

Collections

Graduate School of Natural and Applied Sciences, Thesis