Retaining High Q Factors in Electrode-Less Aln-On-Si Bulk Mode Resonators with Non-Contact Electrical Drive

Abstract

This paper reports on an experimental study of actuation techniques of aluminum nitride on silicon (AlN/Si) heterostructure resonant microelectromechanical systems (MEMS) with both bulk and flexural modes, and comparison of their quality factors (Qs) and energy losses induced by different resonant motion excitation schemes. For AlN/Si MEMS resonators without deposited top metal electrodes, we have devised a new scheme to electrically drive the device, enabled by a non-contact overhanging electrode inducing gradient forces, to replace the otherwise required optical excitation for electrode-less devices. For the bulk mode resonance of AlN/Si resonator at 10MHz, almost equal Q of ~26,000 is obtained for both the new electrical drive and the optical drive, whereas the electrical drive enables the detection of a ~1MHz mode that is not visible when driven optically. For the Si-only device, Q of 257,300 is attained with the non-contact electrical drive, noticeably higher than the Q of 212,225 with the optical drive, suggesting that non-contact electrical excitation results in lower energy dissipation than optical actuation. The present work motivates further studies of transduction mechanisms to achieve higher resonator Qs.