Fabrication and characterization of lithium-niobate thin film MEMS piezoelectric resonators

Abstract

This work proposes single crystal X-cut thin film Lithium Niobate (LN) resonators operating in a shear horizontal (SH 0 ) acoustic plate wave mode to achieve a high electromechanical coupling coefficient. In the fabrication process, we take advantage of the off-the-shelf single crystal X-cut LN dies on which surface micromachining technology is used to fabricate the devices. We design two fabrication process flows, each of which can be roughly divided into three parts. The first part is photolithography, primarily responsible for defining the electrodes and etching holes; this process for fabrication uses two masks. The second part is LN Reactive Ion Etching (RIE) process that defines the device edges. The third part is to etch the silicon dioxide beneath. Wet Hydro Fluoric (HF) chemistry is used to release the thin film structure. This study also reports measurement results of the SH 0 mode LN resonator with the high electromechanical coupling coefficient of 15.8%.