Calibration-free low-drift MEMS piezoelectric accelerometer for high-temperature vibration monitoring

Micro-electro-mechanical system (MEMS) piezoelectric accelerometers offer distinct advantages, including being miniaturized, cost-effective and uniform. However, these accelerometers face challenges with stability and long-term reliability when applied to high-temperature and harsh environments such as oil and gas extraction. To address this issue, this paper focuses on wide-bandgap Sc-doped AlN (AlScN) piezoelectric thin films and a thermal stress isolation design to develop a calibration-free, thermally stable piezoelectric MEMS accelerometer. Firstly, a piezoelectric MEMS accelerometer with wide bandwidth, large range and high linearity is designed by Finite Element Method (FEM). Secondly, the crystallographic, electrical parameters and long-term aging of AlScN at high temperature were systematically characterized, which demonstrated its excellent high-temperature performance. Finally, the mechanism of sensitivity temperature drift was clarified by combining material properties and packaging structure. By designing an on-chip stress isolation structure, the temperature drift of the accelerometer was reduced by 16 times, achieving a piezoelectric MEMS accelerometer with an upper cutoff frequency of 8000 Hz, a range of 500 g, and a low sensitivity temperature coefficient of 0.015%/°C, enabling stable vibration monitoring under extreme environments without additional calibration procedures.