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MEMS

Microelectromechanical systems (MEMS), in which mechanical elements such as beams, gears and springs are integrated alongside electronic circuitry, are the focus of very significant research and commercial effort. Our MEMS research focuses on novel MEMS topologies for use in sensors, and on the effect of dielectric charge accumulation in MEMS.

A large and growing number of sensor systems are based around the use of resonant MEMS which detect shifts in the oscillation frequency/amplitude of a MEMS structure. The change in oscillation may be due to various physical phenomena such as squeeze film damping (pressure sensor), electrolysis (gas/chemical sensor) or structural stiffness (accelerometer). This research uses a Pulsed Digital Oscillator (PDO) topology to actuate self-sustained oscillations, thereby allowing changes in resonant frequency to be monitored by processing the binary output sequence. The selective actuation of higher order resonant modes can improve sensitivity.

The accumulation of dielectric charge in RF MEMS devices, such as RF switches and varactors, can degrade performance and in some cases may cause device failure. This drawback has limited the commercialisation of these devices, which promise higher performance on a CMOS compatible technology platform. This research addresses the effect of dielectric charging in RF MEMS by devising analytical models to describe the charging/discharging mechanisms and develops methods to control the amount of dielectric charge. Many of the charging/discharging mechanisms are not fully understood, so the rigorous analysis performed in this project is an important step towards designing viable RF MEMS devices.

Our principal collaborators on this work are Professor Manuel Dominguez and his colleagues in the Micro and Nanotechnologies group of the Universitat Polytècnica de Catalunya (UPC), Barcelona, and Ray Goggin and his colleagues at the Routers, Protectors and Sensors group at Analog Devices, Ireland.