Segmented electrode excitation of aluminum nitride contour mode resonators to optimize the device figure of merit

Abstract

This paper presents a new electrode configuration for a more efficient excitation of mechanical vibrations in aluminum nitride contour-mode MEMS resonators. We call this technique the segmented electrode excitation. This excitation method results in up to 40% improvement in the figure of merit (FoM) of the resonator, nominally the product of the electromechanical coupling coefficient, k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and quality factor, Q. The segmented electrode configuration is based on the idea of implementing efficient sampling of the charge developed during vibrations, while reducing the electrode coverage. The reduction in electrode coverage ensures that the resonator exhibits a higher Q as interfacial losses are reduced. The efficient sampling enables attaining a k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> comparable to a conventional metal coverage design.