Effect of structural parameters on functional performance of CMUT: a simulation study and analysis

Capacitive micromachined ultrasonic transducer (CMUT) is getting broader attention nowadays, its frequency and the deflection are important parameters because they are closely related to CMUT performance including the resolution, the penetration depth, and the acoustic impedance. Current CMUTs are mainly based on silicon nitride and polysilicon as the membrane materials, understand the frequency versus CMUT structure and the deflection versus the structure and the applied bias voltage are important. Authors have developed a finite element simulation method to investigate the optimal parameters in CMUT design by studying the effects of different structures on the frequency and the deflection. The simulation studied the effects of membrane thickness and top electrode size on the frequency, as well as the effect of voltage on the membrane bending. Results have indicated that smaller radius, thin membrane and thin top electrode as well as large top electrode size are preferred for CMUT design.