Development of Highly Integrated Quartz Micro-Electro-Mechanical System Tilt Sensor

In this paper, we report the research progress of a recently developed quartz micro-electro-mechanical system (MEMS)-based capacitive tilt sensor using bulk micromachining technology. The sensor, which is composed of a sensitive cantilever, proof mass and high-aspect-ratio vertical comb electrodes in wafer thickness, was fabricated using an anisotropic wet etching process on a 100-µm-thick z-cut quartz wafer. A ceramic package was designed for mounting the sensor and integrating the capacitance to a digital AD7746 circuit (Analog Devices). The sensor was mounted on the package using a flip chip method via a AuSn alloy solder. The dimensions of the integrated sensing system are 12 ×12 ×3.2 mm3 and the weight of the system is below 1 g. The measured typical sensor sensitivity is 632 fF/° when the applied voltage is 0.625 V. The peak-to-peak output signal drift is limited to 1 fF in 2 h. Good linearity was achieved in the range of ±1°. High-precision detection at 0.001°, which corresponds to micro-g acceleration, was also demonstrated.