Silicon carbide membranes for micro-electro-mechanical-systems based CMUT with influence factors
An analytical model is developed for evaluating the characteristic parameters of silicon carbide (SiC) based capacitive micromachined ultrasonic transducer (CMUT) under the effect of a high-k dielectric insulation layer. The performance of parallel plate structured CMUT is investigated by considering various widths of the insulation layer, membrane thickness, diameter, and bias followed by validation of results using finite element method (FEM) simulation. Consideration of the fringing effect results in noticeable improvements in device capacitance. This enhancement leads to improvement in displacement due to static bias, signal, and coupling coefficient. The comparative analysis is carried out between hafnium oxide (HfO2) and silicon nitride (Si3N4) insulation layers. CMUT having HfO2 insulation of 500 nm thickness exhibits resonance at 1.62 MHz and displacement of 405 nm. Approximately 20% enhancement occurs in displacement as compared with Si3N4 as insulation.