Study On Tunable Film Bulk Acoustic Resonator Based On Aln

In order to cope with more communication standards and ever-increasing bandwidth requirements,a large number of filters are used in the transceivers of modern wireless communication systems to dispose of increasing transmission frequency bands.As a basic unit of the filter,FBAR has a wide application market.With the substantial increase in the number of RF front-end devices,replacing fixed-frequency filter banks with tunable filters is a highly anticipated solution.In the research of FBAR,the turning characteristic of resonance frequency has always been the focus.The existing tuning schemes are generally based on the control of external conditions such as electric field,temperature and magnetic field,but none of the tuning schemes has yet been commercialized.The controllability of the FBAR tuning range is necessary,in which devices with a smaller tuning range can meet the requirements of a specific highprecision resonance frequency,and a large tuning range can be applied to tuning filters.Hence,the tunable FBAR has great development potential and research significance.This thesis carried out research on tunable FBAR,the specific contents are as follows:Firstly,the fabrication process of FBAR is optimized by using MEMS technology.The principle of FBAR and the application of Al N piezoelectric film in flexible electronic devices are analyzed.The Q value of the prepared FBAR is 1387,with the center frequency is 2.2528 GHz.At the same time,a new preparation method of flexible Al N piezoelectric film was developed by combining with etching process.The flexible piezoelectric film with FWHM of 1.49° can be obtained,and it keeps good piezoelectric effect in bending state.Then the tunable FBAR based on Al N,which is mainly based on temperature and electric field,is studied by using the principle that FBAR is sensitive to external environment.Based on the temperature tuning technology,the FBAR device has a controllable temperature tuning law by inserting PSG temperature modulation layer.The modulation of TCF from-37ppm/? to +19.2ppm/? is realized.Furthermore,a dual-mode FBAR temperature sensor is developed,which can improve the temperature sensitivity and stability of the sensor.It is found that the temperature sensitivity can reach 64.8k Hz/?.Based on the tuning method of electric field,the intrinsic tuning technology and the non-intrinsic tuning technology are studied respectively.Comparing the structure design of internal and external schottky capacitors in non-intrinsic tuning technology,we present the optimization scheme.The tuning performance of the device can be predicted by MBVD simulation,which can reach 3MHz/(MV/m).This study has a certain guiding value for the application and expansion of tunable FBAR technology.