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

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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.