CMUT array element in deep-collapse mode

Abstract

Abstract-Collapse and deep-collapse mode of operations have boosted the pressure outputs of capacitive micromachined ultrasonic transducers (CMUTs) considerably. In this work, we demonstrate a CMUT element operating in the deep-collapse mode with 25 V pulse excitation and without the effects of charge trapping. The fabricated CMUT element consists of 4 by 4 circular cells with 20 µm radius and 1 µm thick plates suspended over a 50 nm cavity. The overall size of the element is 0.190 mm by 0.19 mm. The collapse voltage of the plates is measured to be approximately 3V. By driving the CMUTs with 25V pulses in the deep-collapse mode without any bias, we achieved 1.2 MPa peak-to-peak pressure output on the surface of the CMUT element with a center frequency of 9 MHz and 100% fractional bandwidth. We applied 1000 consecutive electrical pulses with alternating polarity to the element and witnessed no change in the transmitted acoustic pulse.

A Review on Analytical Modeling for Collapse Mode Capacitive Micromachined Ultrasonic Transducer of the Collapse Voltage and the Static Membrane Deflections

“…A summary of advantages and disadvantages of collapse mode operation is in Table 1 . Though the charging effect is more severe than in conventional mode, the charging effect can be decreased by alternating the polarity of the AC pulse [ 37 , 38 ]. The high second harmonic distortion (SHD) of collapse mode could decrease by shaping the input pulse [ 33 ].…”