Tong Yinjie, Han Tao
School of Electronic, Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Micromachines (Basel). 2021 Jan 7;12(1):62. doi: 10.3390/mi12010062.
Energy leakage via anchors in substrate plates impairs the quality factor () in microelectromechanical system (MEMS) resonators. Most phononic crystals (PnCs) require complicated fabrication conditions and have difficulty generating a narrow bandgap at high frequency. This paper demonstrates a pillar-based PnC slab with broad bandgaps in the ultra high frequency (UHF) range. Due to Bragg interference and local resonances, the proposed PnC structure creates notably wide bandgaps and shows great advantages in the high frequency, large electromechanical coupling coefficient (k2) thin film aluminum nitride (AlN) lamb wave resonator (LWR). The dispersion relations and the transmission loss of the PnC structure are presented. To optimize the bandgap, the influence of the material mechanical properties, lattice type, pillar height and pillar radius are explored. These parameters are also available to adjust the center frequency of the bandgap to meet the desirable operating frequency. Resonators with uniform beam anchors and PnC slab anchors are characterized. The results illustrate that the of the resonator improves from 1551 to 2384, and the mechanical energy leakage via the anchors is significantly decreased using the proposed PnC slab anchors. Moreover, employment of the PNC slab anchors has little influence on resonant frequency and induces no spurious modes. Pillar-based PnCs are promising in suppressing the anchor loss and further improving the of the resonators.
通过衬底板中的锚点产生的能量泄漏会损害微机电系统（MEMS）谐振器的品质因数（ ）。大多数声子晶体（PnC）需要复杂的制造条件，并且在高频下难以产生窄带隙。本文展示了一种在超高频（UHF）范围内具有宽带隙的柱状PnC平板。由于布拉格干涉和局部共振，所提出的PnC结构产生了显著宽的带隙，并且在高频、大机电耦合系数（k2）的薄膜氮化铝（AlN）兰姆波谐振器（LWR）中显示出巨大优势。给出了PnC结构的色散关系和传输损耗。为了优化带隙，研究了材料力学性能、晶格类型、柱高和柱半径的影响。这些参数也可用于调整带隙的中心频率，以满足所需的工作频率。对具有均匀梁锚点和PnC平板锚点的谐振器进行了表征。结果表明，谐振器的 从1551提高到2384，并且使用所提出的PnC平板锚点可显著降低通过锚点的机械能泄漏。此外，采用PNC平板锚点对谐振频率影响很小，并且不会引入杂散模式。基于柱状的PnC在抑制锚点损耗和进一步提高谐振器的 方面具有前景。
