Fabrication and measurements of dynamic response of an SOI based non-planar CMUT array

Abstract

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 along with measurement results on individual CMUT cells for transient and steady-state response using a Polytec laser Doppler vibrometer. The measurement results are compared with analytical and 3-D electromechanical finite element analysis using IntelliSuite™. The measured results are in excellent agreement with analytical and FEA results. Measurement results also show that the 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.