Finite Element Simulation Of Capacitive Micromachined Ultrasonic Transducer And Analysis Of The Static And Dynamic Properties Of Its Film

Capacitive micromachined ultrasonic transducer(CMUT)is a kind of ultrasonic transducer based on micro-electromechanical system(MEMS)technology.It has advantages of high bandwidth,easy integration and high sensitivity.Compared with the traditional piezoelectric micro-machined ultrasonic sensors which have many limitations in many aspects,more and more researchers pay attention to the new micro-machined ultrasonic sensors,so capacitive micromachined ultrasonic transducer has great research value and broad application prospects.Capacitive micromachined ultrasonic transducer has two normal working modes.In the transmitting mode,the vibration of the sensor film produces ultrasonic wave,while in the receiving mode,the sensor receives ultrasonic wave to cause the vibration of the film.Vibration film is the core structure of capacitive micromachined ultrasonic transducer.The finite element simulation analysis of the vibration thin film can not only calculate the deformation distribution of the vibration thin film,but also analyze the sensor performance under various vibration conditions.In this paper,the finite element simulation of capacitive micromachined ultrasonic transducer will be carried out to analyze the static and dynamic properties of film deformation and verify the finite element analysis method.The main research work of this paper can be divided into the following parts:Firstly,the piezoelectric micro-machined ultrasonic sensor and capacitive ultrasonic sensor and their research progress at home and abroad are introduced.The basic structure of capacitive micromachined ultrasonic transducer and two normal working modes are described.The electromechanical model of mass spring with parallel plate capacitor of capacitive micromachined ultrasonic transducer is put forward and emphatically expounded.The collapse voltage,electromechanical conversion rate and acceptance mode sensitivity of capacitive micromachined ultrasonic transducer are expounded and deduced.The expression is obtained,and the relationship between the structural parameters and the performance of the sensor is analyzed.Secondly,the finite element analysis software ANSYS workbench17.0 platform is used to complete the modeling,finite element analysis and modal analysis process of capacitive micromachined ultrasonic transducer.The characteristics of the three types of thin film structures are intuitively obtained,and the advantages of diamond-shaped structural films are found.Under the same load conditions,the maximum deformation of the diamond film is only 35.9% of the rectangular film,and the maximum shape variable is significantly different.In the modal analysis,the first-order natural vibration frequency of the diamond structure reaches 1.72 times that of the rectangular structure.A series of static and dynamic performance analysis of capacitive micromachined ultrasonic transducer film deformation,through the DC bias signal and AC signal to control the film to achieve the desired dynamic performance.Finally,the finite element analysis method is used to verify the collapse voltage of capacitive micromachined ultrasonic transducer,the sensitivity of the collapse voltage reached 0.442%.The dynamic performance of capacitive micromachined ultrasonic transducer under receiving state is verified by reverse thinking.The vibration displacement and output current of the film are obtained.The maximum displacement deviation rate is only 2.10%.The correctness and accuracy of the capacitive micromachined ultrasonic transducer finite element analysis method used in this paper are verified.