Research On Frequency-temperature Characteristics Of TPoS MEMS Resonator And Its Application

TPoS microelectromechanical resonators combine the advantages of large electromechanical transduction efficiency of piezoelectric film and low acoustic loss of single crystal silicon,which leads to good performance such as low dynamic impedance and high Q value.Thanks to these advantages,the TPoS resonator is considered as an excellent resonant sensing unit.At present,how to fulfill high precision on-chip temperature compensation scheme has been one of the urgent problems to be solved in the fileld of sensor technology.In this thesis,the temperature-frequency characteristics of the TPoS resonator are investigated,based on which a sensing system with real-time highprecision temperature detection capability is constructed using the TPoS resonator as the core temperature sensing unit.This thesis first analyzes the basic structure and working principle of the TPoS resonator.Afterwards,the theoretical analysis of the temperature-frequency characteristics of the TPoS resonator was carried out and a theoretical model of its temperature-frequency characteristics was established,so as to provide theoretical guidance for device optimization for temperature sensing applications.Finally,doubleand triple-ended-tuning-fork(D/TETF)resonators operating in the first-order out-ofplane flexural vibration mode was designed.The thermal mismatch effect between the composite material layers inherent in the TPoS structure was utilized to achieve a large temperature-frequency coefficient,realizing a highly sensitive temperature sensing unit.Subsequently,the processing flow,device layout drawing and device sample characterization were introduced.Afterwards,this work perform measurement on the fabricated TPoS tuning fork resonators.Firstly,the frequency response of the resonator was measured using open-loop configuration.Then,a closed-loop oscillation circuit was designed according to its frequency response characteristics.The measured results show that,in temperature range of 25℃ to 60℃,the temperature sensitivity of the designed D/TETF resonators were better than-1000 ppm/℃ with resolution of 0.05℃.Moreover,other modules for frequency measurement,frequency-temperature conversion and real-time data display were also designed and realized,combined with the closed-loop oscillator circuit to form a complete temperature sensing system.Finally,this thesis specifically designs the temperature frequency coefficient of the TPoS resonator for different application scenarios.On the one hand,a temperature sensor with ultra-high temperature sensitivity is realized by combining the beat frequency method and the introduction of strain amplification beams;on the other hand,the temperature frequency coefficient of the TPoS resonator is reduced by reducing the electrode coverage and increasing the insulation layer coverage to realize Low temperature drift characteristics.