Design and fabrication of RF MEMS devices for wide-band VHF applications

Abstract

This Ph.D. research work investigates the potential application of PiezoMUMPs technology to the design of a Lateral Bulk Acoustic Piezoelectric MUMPs (LBAW PiezoMUMPs) resonators that can operate in the VHF band. By analysing the effects of resonator size, number of electrode elements, and tether shape on parameters like resonant frequency and Quality factor (Qf). This work is based on analytical, Finite Element simulations, validated by prototype characterisation. Fine tuning through is essential in order to compensate for process related variation, for this reason thermal tuning using both ovenisation as well as on chip electrothermal tuning was investigated. Furthermore, volage tuning was also evaluated. Tuning via ovenisation achieved a tuning range of 300KHz over temperature range of 273 to 573K. Voltage tuning achieved a 30KHz over a range of 1 to 9 V. Electrothermal tuning resulted a 50KHz range for a thermal power of 50mW. This part of the study showed that thermal tuning results in a wider tuning range than voltage tuning. The study also investigates mechanical contact type RF-MEMS switches for VHF band applications, implemented on the same PiezoMUMPs process, in order to achieve a cost-effective wide frequency tuning. In this investigation, several electrostatically actuated switches, having different signal contact profiles were analytically studied and simulated using CoventorWare FEM software. These switches were optimized for different parameters depending on the design geometry and actuator comb fingers. Subsequently, different switch prototype configurations such as 1-way including the deep off option, as well as 2-way structures have been manufactured and characterised.