Zhang Juan, Tan Qiulin, Zhang Lei, Zhao Nan, Liang Xiaorui
State Key Laboratory of Dynamic Measurement Technology, North University of China, Taiyuan 030051, China.
Department of Mechanical Engineering, Taiyuan Institute of Technology, Taiyuan 030008, China.
Micromachines (Basel). 2022 Mar 20;13(3):479. doi: 10.3390/mi13030479.
We proposed a novel Langasite (LGS) bonding method only using high temperature to solve the manufacturing difficulty of the sealed microcavity of pressure sensors. The optimal bonding parameters by comparative experiments were defined as 1350 °C for 3 h. Due to simple experimental conditions, low experimental cost, and be suitable for bonding wafers with various sizes, the method is convenient for popularization and mass-production, thus promoting the development of surface acoustic wave (SAW) devices at high temperatures. Simultaneously, an intact microcavity was observed by scanning electron microscopy, and a tight and void-free bonding interface with a transition layer thickness of 2.2 nm was confirmed via transmission electron microscopy. The results of tensile and leakage experiments indicated that the bonded wafer with the sealed microcavity exhibited a high bonding strength of 4.02 MPa and excellent seal performance. Compared to the original wafer, the piezoelectric constant of the LGS bonded wafer had a reduction of only 4.43%. The above characteristics show that the sealed microcavity prepared by this method satisfies the conditions for fabricating the LGS SAW pressure sensors. Additionally, based on the bonding interface characterizations, the mechanism of LGS bonding has been investigated for the first time.
我们提出了一种仅利用高温的新型硅酸镧镓（LGS）键合方法，以解决压力传感器密封微腔的制造难题。通过对比实验确定的最佳键合参数为1350℃、3小时。由于实验条件简单、成本低且适用于各种尺寸的晶圆键合，该方法便于推广和大规模生产，从而推动了高温表面声波（SAW）器件的发展。同时，通过扫描电子显微镜观察到完整的微腔，并通过透射电子显微镜确认了具有2.2nm过渡层厚度的紧密且无空隙的键合界面。拉伸和泄漏实验结果表明，带有密封微腔的键合晶圆表现出4.02MPa的高键合强度和优异的密封性能。与原始晶圆相比，LGS键合晶圆的压电常数仅降低了4.43%。上述特性表明，用该方法制备的密封微腔满足制造LGS SAW压力传感器的条件。此外，基于键合界面表征，首次对LGS键合机理进行了研究。
