Design and fabrication of quartz micro-electro-mechanical system-based double-ended tuning fork with variable sections

In this paper, we report a novel double-ended tuning fork (DETF) with variable sections. The DETF is fabricated using a quartz micro-electro-mechanical system (MEMS) technique and packaged using the flip chip technique. The central part of the vibration beam is thinned to enhance the force-frequency sensitivity but not decrease the vibration frequency. The mechanical quality factor (Q value) can also be maintained, which determines the mechanical noise performance. Three types of DETF are designed and fabricated with a fixed beam length of 4 mm. The vibration characteristics (vibration frequency, Q value, and equivalent circuit parameters) are evaluated using an impedance analyzer 4294A. The finite element method (FEM) is used to simulate the natural frequency and force-frequency sensitivity. For the natural frequencies, the experimental results agreed well with the simulation results. High Q values are achieved for all the DETFs, which are 9924, 7083, and 6335. By multiplying the force-frequency sensitivity (ΔF) by the measured Q values, the performance of the new DETF structure can be improved by 1.9 times.