Research On Thin Film Bulk Acoustic Resonators For Micro-mass Sensing

Compared with the common mass sensor,quartz crystal microbalance(QCM),the micro-mass sensor based on film bulk acoustic resonator(FBAR)has advantages of small volume,low loss,high sensitivity,high quality factor(Q),high operating frequency,good temperature stability,compatibility with semiconductor processes,etc.,show broad application prospects.In this paper,we focused on the research of FBAR for micro-mass sensing,and designed three different FBAR structures.By selecting the material of each film layer,simulating the structure size and exploring the preparation process,the FBAR structure for ng-quality sensing is prepared finally,which lays a foundation for the research of subsequent biosensors.The research work of this paper can be summarized as:1.The effects of structure,piezoelectric film and electrodes on the performance of FBAR devices were analyzed.Three FBAR structures for micro-mass sensing were designed and the materials used for each film layer were determined.The finite element software is used to simulate and optimize the designed structure,and the characteristic frequency,electromechanical coupling coefficient(keff)and Q value of each structure are obtained.Finally,the performance of the three structures is summarized and selected,and the most suitable structure is selected for preparation.2.Design a mask and use MEMS technology to prepare FBAR for micro-mass sensing.The lithography process operation and precautions are mainly introduced.The preparation process of FBAR is introduced in detail,and the FBAR structure with different top electrodes is obtained.3.The FBAR structure for micro-mass sensing was tested using an impedance analyzer.The shape,size,and thickness of the top electrode can affect device performance.The test results show that the shape of the upper electrode is pentagon,the area size is 60000?m~2,and the thickness is 0.03?m,the performance of FBAR is better;In addition,the sensor with different top electrode loads was tested by the impedance analyzer to calculate the sensitivity of the sensor.The theoretical value is 3.97×10~5 Hz.cm~2/ng.