MEMS电容式超声传感器设计

Design of MEMS Capacitive Ultrasonic Transducer Based on Anodic Bonding Technology

在传统的电容式超声传感器(CMUT)制造过程中,用低压化学气相淀积技术形成的氮化硅薄膜残余应力大且机械性能难以预知。为此,设计了一种基于阳极键合技术的CMUT,传感器薄膜和空腔分别定义在均匀性好、残余应力低的SOI片和玻璃片上。建立了一个简化的分析模型对该结构进行机械性能分析,采用有限元分析软件ANSYS仿真验证该所建立的分析模型并预估传感器的性能。利用ANSYS静电-结构耦合仿真给出了塌陷电压。介绍了敏感单元的工艺流程。所设计的传感器频率为1.48 MHz,灵敏度为0.24fF/Pa,塌陷电压为70V,量程为48kPa。

In traditional micromachined capacitive ultrasonic transducer （CMUT） fabrication process, the silicon nitride membrane is deposited by low pressure chemical vapor deposition（LPCVD）, which result in unpredictable mechanical properties and more residual stress in the membrane. Therefore a navel CMUT structurebased on anodic bonding technology is designed . The transducer membrane and cavity are defined on an even thickness and low re- sidual stress SOI wafer and glass wafer, respectively. A simplified analytical model is established to describe the me- chanical properties of the structure. Finite element model in ANSYS is also conducted to verify the analytical model and evaluate the performance of the device. The collapse voltage is simulated by coupling analysis of electrostatic- structure. Process flow is presented. The frequency of the structure is 1.48 MHz, sensitivity is 0.24 fF/Pa, col- lapse voltage is 70 V, range is 48 kPa.