Spurious mode suppression in SH0 Lithium Niobate laterally vibrating MEMS resonators

Abstract

This paper reports on the development of a spurious mode suppression technique for shear horizontal (SH0) mode Lithium Niobate (LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) laterally vibrating MEMS resonators. The method employs an optimized overlapping length between adjacent interdigitated electrodes to modify the presence of stress and electric field distribution in the resonator body, subsequently enabling near zero electromechanical coupling (k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) for the higher order transverse spurious modes. The technique can be applied to devices with different center frequencies without additional fabrication steps by lithographically modifying the electrode configuration. It has resulted in the first demonstration of LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -LVRs that features an unprecedented spectral range of spurious-free response (130-170 MHz). In addition, the fabricated spurious-mode-free device, with an orientation of 10° to -Y-axis on the X-cut plane, has shown a k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 20.6%, a quality factor (Q) of 1064, and thereby an exceptionally high figure of merit (FoM) of 220.