Highly sensitive strained AlN on Si(1 1 1) resonators

In this study, we report two methods to fabricate freestanding single-crystalline aluminium nitride micromechanical device structures on Si(1 1 1) substrates. A method based only on Si etching techniques is demonstrated, and the differences with the conventional process are detailed. The mechanical properties of the released AlN structures are characterized by resonance measurements and micro-Raman spectroscopy. An enhancement of the resonant frequency and quality factor of resonant structures, and thus the sensitivity, is proposed using epitaxial AlN. This high quality material, highly strained due to thermal mismatch with Si substrate, allows the fabrication of improved high sensitivity AlN-based micro/nano electro-mechanical systems and sensors.