Smoothing the way towards miniaturized MEMS AlN-based piezoelectric transformers

This work presents the electromechanical characterization and design of a Piezoelectric Transformer (PT) made on a Silicon-On-Insulator (SOI) structure through a bulk micromachining process exploiting low-frequency flexural-modes. The footprint area of the device is less than 3.5 mm2. The purpose of this work is to show the enhancement obtained with respect to prior state of the art in terms of quality factor and voltage gain for the fundamental mode. As matter of fact, the presented device, achieves 2-factor ∼71 at environmental pressure, being almost 6 times greater with respect to the one of the same membrane with double radius and almost 4X footprint area. The step-up ratio at environmental pressure is ∼25mV/V, but it increases at 250mV/V when the device is operated in a vacuum chamber, thus being more than 20X times higher the step-up ratio achieved for the same membrane with double radius in vacuum environment.