几何尺寸和锚点辅助结构对宽度伸张模态微机械谐振器能量损耗影响机理的研究

Quality factor (Q) is the most critical factor limiting the performance improvement of micromechanical resonators. High Q is desirable for realizing low-phase-noise micromechanical resonator-based oscillators, as well as achieving high-resolution resonant sensors. Q of a micromechanical resonator is determined by the energy losses from each energy dissipation mechanism. Anchor loss is one of the most dominant energy loss mechanisms for most micromechanical resonators. Targeted on obtaining the optimized design of micromechanical resonators for reducing their vibrating energy losses, it’s proposed to reveal and analysis the effects of geometry and accessory structures on energy dissipation mechanisms in width-extensional mode micromechanical resonators. With an optimized design of geometry, the mechanical vibrations at the joint areas of the resonant structures and the anchors will be largely reduced, resulting in less energy losses to the substrate through anchors. In order to reduce the anchor losses, optimized anchor designs using accessory structures for micromechanical resonators are explored. Effect of the accessory structures on the anchor losses of the micromechanical resonators are investigated. The accessory structures could tune the node points to the joint regions of the anchors and substrate. Therefore, the mechanical vibrating energy will be trapped in the resonant structures and minimizing their propagations to the substrate, improving the Q of the micromechanical resonators. Aiming to reveal and investigate the effects of geometry and accessory structures on energy dissipation mechanisms in width-extensional mode micromechanical resonators, it provides a direction and reference for developing high-Q micromechanical resonators.

品质因子（Q值）是限制微机械谐振器性能提升的最关键因素。高的Q值可以降低振荡器频率输出的相位噪声，以及提高谐振式传感器的频率分辨率。微机械谐振器的Q值取决于它的能量损耗机制。锚点损耗是大多数微机械谐振器最主要的能量损耗机制之一。本项目系统开展基于氮化铝-单晶硅材料的宽度伸张模态微机械谐振器能量损耗机理的研究：（1）探索几何尺寸对宽度伸张模态微机械谐振器能量损耗的影响机理，提出几何尺寸优化设计方案，减小谐振振子与锚点结构连接处的机械振动，降低振动能量通过锚点向衬底的传播；（2）揭示锚点辅助结构对微机械谐振器锚点损耗的影响规律，提出辅助结构优化设计方法，将振动节点设计在锚点与衬底连接处，进而将机械振动能量局限在谐振振子结构中，减小锚点损耗，提高微机械谐振器的Q值。本项目旨在揭示几何尺寸以及锚点辅助结构对宽度伸张模态微机械谐振器能量损耗的影响规律，为研制高Q值微机械谐振器提供指导思路。

锚点损耗和热弹性阻尼是大多数微机械谐振器能量损耗的最主要来源。降低锚点损耗和热弹性阻尼，进而提高微机械谐振器的品质因子（Q值），对提升微机械振荡器的频率输出精度以及微机械谐振式传感器的频率分辨率至关重要。该项目研究了几何尺寸对宽度伸张模态微机械谐振器锚点损耗和热弹性阻尼的影响机理，提出微机械谐振器几何尺寸优化设计方案，将谐振器热频率远离其机械谐振频率降低热弹性阻尼，并将谐振振子与支撑梁相连地方调节为近似节点位置，降低振动能量通过锚点向衬底的传播；揭示了锚点辅助结构对微机械谐振器锚点损耗的影响规律，提出辅助结构优化设计方法，通过辅助结构设计调节振动节点至锚点与衬底连接处，进而将机械振动能量局限在谐振振子结构中，减小锚点损耗，提高微机械谐振器的Q值。采用上述技术方案，所研究的氮化铝宽度伸张模态微机械谐振器的Q值从10562提高到了33041。该项目的研究，为高Q值微机械谐振器的研制提供了设计思路和理论依据，可为无线通信、汽车电子以及工控安防领域时钟芯片的发展提供技术支撑。