A micromachined accelerometer with on-chip snap-lock assembly for capacitance enhancement via gap reduction

A micromachined capacitive accelerometer employing an electrothermal drive assembly and mechanical locking structure is presented. Such a structure is designed to move the stator electrodes after fabrication, and maintain them at the desired position, thereby reducing the sensing gap and improving the capacitor response. The post-processing assembly of the capacitor’s electrodes is driven by an electrothermal mechanism, and the assembled electrode position is maintained by a mechanical snap-locking structure. To demonstrate the effectiveness of the design concept, we fabricated a proof-of-concept device and a reference device reproducing a conventional design, using industrial silicon-on-insulator micromachining technology. The experimental results showed that the designed assembly and locking structure can achieve electrode position adjustment and maintain the assembly state stably. The device's capacitive response was characterized using a capacitance-voltage test and an electrostatic driving equivalent-acceleration analysis. The proposed accelerometer exhibits a larger capacitance variation than the corresponding reference device, thereby demonstrating enhanced capacitance sensitivity by enabling the complete removal of traditional fabrication limits on the capacitance-to-device-thickness ratio. These results open the path to high-performance, low-cost commercial silicon micro-accelerometers without modifying fabrication or testing procedures.