基于硅-玻璃键合工艺的微惯性器件的材料热失配应力表征

Characterization of thermal mismatch stress of micro-inertial devices based on silicon-glass bonding process

基于硅-玻璃键合工艺实现敏感结构和衬底相接是微惯性器件的主流工艺方案之一。硅和玻璃热膨胀系数不同,在惯性器件环境工作温度发生变化时,硅玻璃接触表面会产生热应力,该应力严重影响器件的性能。为了测量异质材料间的热失配应力以及键合锚点尺寸对应力的影响,本文提出了一种以悬臂梁作为测试结构的锚点形变测量和数据处理方法,用于表征器件的工艺热失配应力。根据仿真结果将锚点设计成切块形式以减小最大应力和结构形变。测试结果表明,对于边长为600,400和200μm的锚点,悬臂梁相对锚点的平均离面位移分别为0.43,0.30和0.20 nm/℃;结果具有良好的重复性。该结果说明锚点热形变与锚点的大小直接相关,这对MEMS惯性结构以及工艺设计改进具有重要的意义。

Silicon-glass bonding technology is critical to the development of durable micro-inertial devices.Because the thermal expansion coefficients of silicon and glass are different,thermal stress is produced on the silicon-glass contact surface when the operating temperature of the inertial device changes.This can have a serious effect on the performance of the device.Therefore,an understanding of the extent of thermal mismatch stress between these heterogeneous materials and the effect of bonding anchor point size on stress are important for the improvement of the structure and process design of these devices.In this paper,a method of anchor deformation measurement and data processing using a cantilever beam as the test structure is proposed to characterize the process thermal mismatch stress of the device.The simulation results indicate that anchor points designed in block form reduce the maximum stress and structural deformation.For anchor points with side lengths of 600μm,400μm,and 200μm,the average off-plane displacements of the cantilever beam relative to the anchor points are 0.43 nm/℃,0.30 nm/℃and 0.20 nm/℃,respectively.These results have good repeatability.Our results show that the thermal deformation of anchor points is directly related to the size of the anchor points,and this has important research significance for the improvement of MEMS inertial structure and process design.