面向亚ng精度MEMS加速度计的水平准零刚度结构研究

高精度加速度计在地球物理科学、重力资源勘探与辅助导航等领域有广泛的应用需求。相比于传统金属或石英簧片加速度计，MEMS加速度计在尺寸、重量及成本方面优势明显。然而，由于MEMS结构难以实现低本征频率等瓶颈的限制，现有MEMS加速度计尚不能满足诸多地球物理应用的精度要求。本项目拟借鉴隔振系统中常用的正、负刚度抵消降低本征频率的思想，开展MEMS轴向拉、压复合梁水平准零刚度结构研究，揭示结构的刚度调控机理及多悬臂梁组合几何构型对交叉轴刚度的作用机制；开发垂向穿透刻蚀与侧向精细调节组合加工方法实现结构精确制备与刚度调控；通过加速度计集成检验结构的MEMS工艺兼容性。目标是化解MEMS结构低本征频率与可加工性、交叉轴刚度之间的矛盾，研制本征频率低于1Hz，交叉轴刚度比大于10000的MEMS弹簧-振子结构，为本底噪声优于0.1ng/√Hz的MEMS加速度计的研发提供支撑。

High-precision accelerometers have found wide applications in geophysical sciences, resource explorations and gravity-aided navigation. MEMS accelerometers have advantages in size, weight and cost compared with the traditional accelerometers with metal or quartz springs. However, existing MEMS accelerometers are not precise enough for most geophysical applications, due to challenges in the realization of low-frequency spring-mass structure. The project plans to study a horizontal quasi-zero-stiffness structure from the concept of counteracting positive stiffness using negative stiffness, which has been verified in shock isolation systems. Firstly, the mechanism of the structure including the controlling of the stiffness and the relationship between the geometrical configurations of the beams and the cross-axis stiffness will be studied theoretically. Afterwards, a novel fabrication method will be developed, which combines a deep reactive ion etching (DRIE) process for through-wafer etching and a reactive ion etching (RIE) process for precise lateral thinning of the beams for adjusting the stiffness. Finally, the structure will be integrated with a MEMS accelerometer for testing the compatibility. The project aims at developing a novel processable low-frequency MEMS spring-mass structure with high cross-axis stiffness. The targets include that a resonant frequency is lower than 1 Hz, and the ratio between the cross-axis stiffness and sensitive stiffness is larger than 10000, to support the development of MEMS accelerometers with self-noise better than 0.1ng/√Hz.