Research On High Performance First-order Lamb Wave MEMS Resonator Based On AlN-on-Si Structure

Thin-film Piezoelectric-on-silicon(TPoS)resonator is a new type of piezoelectric MEMS resonator,which is featured by high quality factor and high electromechanical transduction efficiency.Due to these advantages,TPoS resonator is considered as a promising resonant unit for realizing high-performance RF oscillator,and recently becomes a hot spot in the research field of MEMS resonators.In addition,TPoS resonator technology is suitable for realizing different resonant frequencies on a single wafer,which benefits forming integrated multi-resonator array,in line with the future development trend of multi-frequency,miniaturized frequency sources.At present,RF TPoS resonators mostly adopt Lamb wave mechanical vibration modes.Therefore,this thesis investigates a group of TPoS resonators operating in different Lamb wave modes,with the aim of realizing high performance RF oscillators.Firstly,this thesis introduces the research background and development of Lamb wave mode TPoS resonators.Then the working principle and key design parameters and equivalent circuit model of TPoS resonators are analyzed and discussed.Specifically,the theoretical model of Lamb wave mode TPoS resonator is compared with 3D simulation model based on finite element analysis.The differences of vibration modes and equivalent circuit parameters between the two models are also analyzed and discussed.Based on the results from theoretical and simulation models,this work designs several groups of Lamb wave mode TPoS resonators with different resonant frequencies,which are subsequently fabricated and characterized.Next,this work uses the vector network analyzer to perform the S-parameter measurement for the fabricated TPoS resonators,from which the equivalent circuit parameters are extracted.This thesis investigates the variation trend of key parameters such as resonant frequency,quality factor,dynamic resistance and dynamic capacitance in different TPoS resonators.It is shown that reducing the interfinger electrode spacing is beneficial to improve the electrical performance of first-order Lamb wave TPoS resonators.Finally,this thesis utilizes Lamb wave TPoS resonators as the core components to complete the design of RF oscillator.Optimization of key parameters such as dynamic resistance,dynamic capacitance,quality factor are performed,constructing the frequency selection network.The discrete transistor is used as the amplifier to form a complete RF oscillator.The measured results show that the RF oscillator based on Lamb wave mode TPoS resonators are promising for future development.