Design and fabrication of micromachined radio-frequency cavity resonators

Abstract

Resonators are used almost in every wireless communications applications and play an important role in the performance of these systems. At radio frequencies, for high performance applications, realization of high-Q resonators is required. Furthermore, in the near future, integration of RF resonators with rest of the system is intended. This thesis describes the design and fabrication of a type of radio-frequency MEMS cavity resonator operating in the frequency range of 2-3 GHz. The fabricated resonators are small in size so that they allow the integration of a whole system on a single-chip. The cavity is realized by selectively removing (etching) silicon substrate using standard MEMS techniques. The resonator is based on creating a low-loss inductor by enclosing the inductor in a metal-coated cavity and then resonating it with either a fixed or tunable high-Q capacitor. In this thesis, formulas for the inductance and the Q-factor of the cavity are derived and a number of resonators are fabricated and measured. The Q-factors of the measured cavities were found to be in the range going up to 25- 30. The obtained results are promising and showed that on-chip resonators with Q-factors higher than 30 can be realized based on this design and fabrication technique at this frequency range.