Dynamic analysis of an SOI based CMUT

An SOI based hyperbolic paraboloid geometry capacitive micromachined ultrasonic transducer (CMUT) array has been fabricated to realize a frequency independent constant beamwidth broadband beamforming capability. Detailed fabrication and packaging techniques are presented. A Polytec laser Doppler vibrometer has been used to measure the transient and steady-state response of individual CMUT cells. The measured dynamic response results are in excellent agreement with analytical and 3-D electromechanical finite element analysis results. Experimental measurement also shows that the fabricated CMUTs exhibit a flat bandwidth within the specified frequency range. SEM inspection also shows very close agreement between mask features and fabricated geometry that ensures reproducibility of the device with a high degree of fidelity. The CMUT array has been designed for automotive blindspot detection application and works in the 113-167 kHz range.