Investigation of Different Membrane Materials Effects in CMUT Membrane Behaviour

Research on Capacitive Micromachined Ultrasonic Transducers (CMUT), which is MEMS-based new transducer technology compared to piezoelectric in ultrasound applications, has recently increased. It is an important fact that micro and nano technologies provide convenience in many areas. CMUT technology has many advantages, such as its small size, the ease of integration with electronic materials and its compatibility with 2-dimensional geometries. In this study, the effect of different membrane material properties on displacement and output pressure of the CMUT membrane was investigated by assuming that it works in CMUT transmission mode and in the water media. SiC, Si, diamond, Si₃N₄, and polysilicon were used as membrane material. The membrane radius and thickness were selected as 60 μm and 2.6 μm, respectively. Collapse voltage and impedance values were calculated according to the structural properties of these materials. In addition, the mechanical structure of CMUT was taken into consideration and modeling was performed. Using this model created in the SIMULINK, the displacement and output pressure of CMUT membrane under various DC and AC voltages were analyzed. Under the same DC voltage, silicon membrane had the highest displacement and diamond membrane had the lowest displacement. Square shape wave was used as the AC excitation signal because the square wave was more efficient than the others. Some properties of the AC signal were changed and their effects were investigated. The most suitable material and working environment were tried to be found. Moreover, Si₃Ni₄ membrane behavior also investigated under different electric field to understand effects of electrode size using same model in air. As a result, this study aims to contribute to efficient CMUT design and determination of optimum parameters and membrane material selection for various applications in the immersion and air.