Research on a Frequency-Change-Type High-Sensitivity MEMS Acceleration Sensor

本研究利用弯曲振子的共振频率变化，研制出一种高灵敏度的MEMS加速度传感器。利用有限元法设计了传感器元件，并进行了试制。1.压电弯曲振子作为高灵敏度力传感器（1）新研制的单晶硅弯曲振子作为高灵敏度力传感器，通过在振子的中心臂上采用Au上电极、PZT压电薄膜和Ag下电极组成的三明治结构，电驱动第一离面振动模式。（2）上电极分为两部分，分别用于驱动和监测。2.加速度传感器的结构和特性（1）传感器元件由振动器、质量块、支撑杆和用于夹紧的框架组合而成，用作单轴传感器，用于检测沿y轴沿着的加速度。（2）由于支承刚度小，所以采用了高灵敏度的悬臂式支承杆。（3）传感器元件的体积约为4.0 × 4.8 × 0.5 mm^3。（4）加速度沿着z轴的影响约为0. 15%，沿沿着x轴的值几乎为0%。（5）实验测得传感器元件的谐振频率为23.1825kHz。（6）实验测得的传感器灵敏度约为4, 000 ppm/G。（7）该传感器还可应用于利用重力绕x轴的倾角传感器，加速度传感器也可由压电单晶实现。因此，良好的温度特性和高效率的驱动器将被期望。将来可以设计用于检测多轴加速度以及与另一传感器组合的传感器结构。

A high-sensitivity MEMS acceleration sensor utilizing the resonance frequency change of a bending vibrator is developed in this research. The sensor element is designed by using the finite element method, and manufactured for trial. The obtained results are summarized as follows.1.Piezoelectric Bending Vibrator as High Sensitivity Force Sensor(1)The newly-developed bending vibrator made of single crystal silicon acts as a high-sensitivity force sensor, and the first out-of-plane mode of vibration is driven electrically by using the sandwich structure consisting of Au upper electrode, PZT piezoelectric film and Ag lower electrode on the central arm of the vibrator.(2)The upper electrode was divided into two parts, and these are used for driving and monitoring respectively2.Construction and Characteristics of Acceleration Sensor(1)The sensor element is constructed by combination of the vibrator, mass, support bars and frame for clamping, and is used as a 1-axis sensor for detection of acceleration along the y axis.(2)The bent-type support bars are used for high-sensitivity because of small support stiffness.(3)The volume of sensor element is about 4.0 × 4.8 × 0.5 mm^3.(4)The effect of acceleration along the z axis is about 0.15%, and the value along the x axis is almost 0%.(5)The resonance frequency of the sensor element was estimated about 23.1825kHz experimentally.(6)The sensor sensitivity obtained experimentally is about 4,000ppm/G.(7)The sensor is also applied to an inclination angle sensor around the x axis by use of gravity.The acceleration sensor can be also realized by piezoelectric single crystals. Therefore good temperature characteristic and high efficient drive will be expected. The sensor structures for detection of multi-axis acceleration and for combination with another sensor may be devised in the future.