An efficient electrostatic actuation model for MEMS-based ultrasonic transducers with fringing effect

In this paper an improved analytical model of electrostatic force for capacitive micromachined ultrasonic transducer (CMUT) has been carried out. These findings are consistent with Landau's method for CMUT fringing field capacitance modeling. The behavior of electrostatic force is investigated for parameters such as the top electrode's diameter, gap separation, actuation layer thickness, and bias applied to CMUT. Due to a significant degree of force creation, a CMUT cell having silicon carbide (SiC) as actuation material is capable of generating high power ultrasonic waves, with approximately 20% improvement over a silicon nitride (Si3N4) counterpart. Introducing an insulation layer in the capacitive cell improves sensitivity and enhances device safety to operate at higher voltages and temperatures. For various insulating thicknesses, a detailed study has been carried out for isolation. The findings of the investigation using the finite element technique (FEM) and the suggested analytical model accord well. The results are also further corroborated by published experimental results.