Reduction of Motional Resistance Using Piezoelectric on Silicon MEMS Disk Arrays for Ambient Air Applications

This paper presents the implementation of a piezoelectric contour resonance mode in a micro-electro-mechanical (MEM) disk resonator array, fabricated using a low-cost, commercially available MEMS technology. The resonator operates in a Button-like (BL) mode, which is suitable for a fully differential piezoelectric transduction mechanism. Compared to other modes, such as the anti-symmetric (AS) mode and the Higher wine glass (HWG) mode, the BL mode offers a higher quality factor (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i>) and a reasonable coupling coefficient (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k_{t}^{2}$</tex-math> </inline-formula>) for the same perimeter around the disk device. The mechanical coupling and excitation of a parallel array of nodal point-coupled piezoelectric disk resonators significantly reduce the motional resistance (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_m </i>) of the vibrating disk MEMS resonator, making the BL mode highly attractive due to the achieved performance improvements. The implementation of this method with three resonators results in an effective motional resistance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$101~\Omega $</tex-math> </inline-formula> at 32 MHz under ambient air conditions. This value is approximately 3.9 times lower (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q_ul </i> normalized) than the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_m </i> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$822~\Omega $</tex-math> </inline-formula> exhibited by a single contour mode disk resonator. Additionally, an unloaded quality factor (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q_ul </i>) of 8,230 is observed when operating at 0dBm power in ambient air. Notably, these enhancements are achieved while maintaining an effective <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q_{ul} \gt 10,000$</tex-math> </inline-formula>, as measured in vacuum conditions, along with notable power-handling capabilities in both ambient air and vacuum environments. This work also investigates two other contour resonance modes with the same design considerations to further validate the proposed methodology. [2025-0006]