CD Laboratory for Piezoelectric Silicon MEMS with Enhanced Sensitivity and Responsivity

This CD Laboratory researches piezoelectric microelectromechanical sensors and actuators (PiezoMEMS). The aim is to significantly improve the sensitivity of PiezoMEMS by investigating noise sources in piezoelectric materials and components and the responsivity of PiezoMEMS by investigating non-linear bi-stable architectures with mechanical deflections of several tens of micrometres.

Microelectromechanical systems (MEMS) are one of the hidden pillars of our modern data- and information-driven world. MEMS are microscopic devices with the ability to measure or detect observable quantities of their environment, interpret and analyse the measurements (e.g. with integrated electronics to provide a certain intelligence) and influence or act on their environment in a specific way. This bi-directionality of MEMS, perceiving the environment on the one hand and influencing it on the other, is expressed by two different terms: sensors and actuators.

Silicon-based MEMS enable, for example, pressure sensors in automotive applications, motion sensors in games consoles and smartphones or cochlear implants. The latest developments are penetrating application areas such as autonomous vehicles, real-time monitoring of chemical processes, remote surgery, augmented reality and many more. A major challenge here is the use under a wide range of environmental conditions and increasing miniaturisation.

Piezoelectric MEMS (PiezoMEMS) use the change in electrical polarisation and thus the occurrence of an electrical voltage on solids when they are elastically deformed. Aluminium nitride (AlN)-based PiezoMEMS are generally characterised by a simple, cost-effective design and provide robust behaviour even in difficult environments such as liquids.

This CD Laboratory therefore investigates fundamental research questions inspired by the limitations of PiezoMEMS to bridge the gap between scientific knowledge and applications.

Particularly with regard to miniaturisation, MEMS sensors require extremely low intrinsic noise in their electrical output signal in order to achieve high signal-to-noise ratios. Intrinsic noise sources are not sufficiently understood, especially in piezoMEMS sensors, and are closely related to the microstructure of the piezoelectric material. Therefore, this CD Laboratory seeks to develop a better understanding of noise sources in AlN-based piezoelectric MEMS sensors by investigating the relationship between material properties, fundamental noise mechanisms and dissipative energy loss mechanisms.

Miniaturisation also leads to very small mechanical deflections in the sub-µm range, especially in piezoMEMS. Therefore, the non-linear dynamic-mechanical behaviour of bi-stable PiezoMEMS actuators with exceptionally high deflections in the range of several 10 µm will be investigated as a further focus.

The results will stimulate research and development of new PiezoMEMS devices in the MEMS semiconductor industry, so that both MEMS manufacturers and, of course, consumers will benefit from the groundbreaking research in this CD Laboratory.