Microfabrication of piezoelectric MEMS based on thick LiNbO₃ single-crystal films

Microfabrication procedure of piezoelectric micro electro-mechanical systems based on 5 μm thick LiNbO₃ films on SiO₂/Si substrate at wafer scale including deep dry etching of thick LiNbO₃ films by implementing pulsed mode of Ar/SF₆ gas was developed. In particular, two (YXlt)/128°/90°LiNbO₃-Si cantilevers with tip mass were fabricated and characterized in terms of resonance frequency (511 and 817 Hz), actuation and acceleration sensing capabilities. The quality factor of 89.5 and the electromechanical coupling of 4.8% were estimated from measured frequency dependency of electrical impedance, fitted by using Butterworth-Van Dyke model. The fabricated piezoelectric micro-electro-mechanical systems have demonstrated highly linear displacement with good sensitivity (5.28 ± 0.02 μm V⁻¹) as a function of applied voltage and high sensitivity to vibrations of 667 mV g⁻¹ indicating a suitability of the structure for actuation purposes and for acceleration or frequency sensing with high precision, respectively.