Dual-Mode AlN-on-Silicon Micromechanical Resonators for Temperature Sensing

Abstract

In this paper, we present dual-mode (DM) AlNon-silicon micromechanical resonators for self-temperature sensing. In-plane width-shear (WS) and width-extensional (WE) modes of [110]-oriented silicon resonators have been used as alternatives to first-and third-order modes to enhance DM temperature sensitivity by engineering device geometry, which reduces inherent beat frequency f b between the two modes. This configuration provides a 50× improvement in temperature coefficient of beat frequency (TC f b ) compared with single-mode temperature measurement and eliminates the need for additional frequency multipliers to generate f b from its constituents.[100]-oriented WS/WE resonators provide 4× larger TCF difference between modes ( TCF) than first and third widthextensional resonators, which further contributes to TC f b enhancement. WS/WE mode resonators also demonstrate the capability of operating as a temperature-stable reference f b . The proposed modes for DM operation have high Q and low motional resistance, and are 180°out-of-phase when operated in two-port configuration, thus enabling mode-selective low-power oscillator interfacing for resonant temperature sensing.

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