AIN Lamb Wave Resonators On Flexible Substrates

Flexible electronic devices have advantages of low cost,light weight,good bending,biocompatibility among others.As an essential part of the flexible electronic systems,flexible MEMS devices also attract much attention.So far,there have been many flexible MEMS devices reported,such as thin film bulk acoustic resonators,electrostatic actuators,transducers and so on.MEMS Lamb wave resonator,as a new technology,has been developed.However,the complex manufacturing process discourages the fabrication of flexible and highperformance LWR devices.Therefore,it would be a tremendous benefit if LWR devices can be fabricated at low cost on a flexible substrate.Compared with thin film bulk acoustic resonators and other MEMS devices,LWRs feature multi-frequency on a single chip and are competent in versatile frequency control components.In this work,aluminum nitride(AlN)LWRs with three different topologies were fabricated on one single chip and were simultaneously transferred to a PET membrane using a polydimethylsiloxane(PDMS)film.Firstly,in this thesis,the basic theory of piezoelectric resonator and the design principle of LWR are introduced.The equivalent circuit model is introduced to analyze the parameters of the Lamb wave resonator.The dissertation also introduces the selection of piezoelectric thin film materials and the fabrication methods of flexible devices.Then,the thesis introduces the fabrication process of the flexible Lamb wave resonator.The structural characteristics and finite element simulation model of LWRs with three different structures are analyzed.The work explains the method of the LWR layout design using software.It also describes the process of making the air cavity on the flexible substrate by nanoimprinting.The transfer platform set-up and the method of transferring AlN film to the flexible substrate are also described.Finally,the electrical performance of the flexible LWRs with three different configurations is tested,including under different bending conditions and temperature influence.The test result of the flexible LWR is compared with the LWR based on the silicon substrate.