Evaluation of Resonance Characteristics Change of Silicon Resonators Due to Surface Treatment

Abstract

Mechanical resonators are applicable to sensors owing to their vibration characteristics. When a mechanical resonator is used as a sensor, the Q factor of resonance is a very important characteristic for achieving a high sensitivity of the resonator. Several trials have been reported to improve the Q factor by surface treatment. However, how the physical or chemical state of the resonator surface affects the Q factor has not yet been clarified. In this study, we examined the effect of the surface state on the Q factor. From experiments for examining surface-treated samples, we found that the Q factor increases with reactive ion etching (RIE) with CF4 gas, and decreases with Ar or O2 gas. To evaluate the effect of the surface state on the Q factor, the surface free energy and chemical bond state changes of the resonator surface were measured. From the result of the experiments, it was proved that lower surface free energies result in larger Q factors.