Fringing capacitance and tolerance of DRIE effect on the performance of bulk silicon comb-drive actuator

A bulk silicon comb-drive actuator with low driving voltage and large displacement is presented in this paper. The bulk silicon comb-drive actuator is fabricated by a simple bulk micromachining process based on the low temperature Au–Au bonding technology. A cascade folded beam is designed to improve the displacement of comb-drive actuator at low driving voltages. The instability of the whole system decreases by utilizing unequal wide comb fingers design. The fringing capacitance and the fabrication tolerances together with their effects on the performances of the comb-drive actuators are also discussed. The measurement results show that the capacitance change rate and the displacement change rate of the comb-drive actuator are 1.5 fF/V² and 0.125 μm/V², respectively. The displacement of the actuator can reach 28.5 μm at 15 V driving voltages. The experimental results of the comb-drive actuator are in good agreement with the modified theoretical predictions.