The slope effect of a capacitive resonator profile fabricated by a DRIE process on the performance of an MEMS disk resonator

Abstract

The thickness of a capacitive disk resonator can be increased by selecting a deep reactive ion etching (DRIE) process for reducing motional resistance. However, the DRIE process sometimes causes MEMS capacitive resonators to have a non-ideal profile. In this paper, the slope effect of a resonator profile fabricated by a DRIE process on the capacitance, electrostatic force, electrical stiffness, motional resistance and output current of the capacitive resonator is analyzed. The relation curves between these parameters and the sloped angle are obtained theoretically. The results show that the capacitance, electrostatic force, electrical stiffness and output current decrease as the sloped angle increases, but the motional resistance obviously increases. By capturing the electric field distribution of a capacitive resonator with different ratios of the gap to thickness by using FEM software ANSYS, the effects of slope angle and thickness on the natural frequency of the resonator are investigated. The analyzed results can provide the theoretical basis for designing high-performance MEMS disk resonators fabricated by the DRIE process.