A 2D Capacitive Micromachined Ultrasonic Transducer (CMUT) Array with Through-Glass-Via Interconnects Fabricated Using Sacrificial Etching Process

A two-dimensional (2D) transducer array is an integral part of a three-dimensional (3D) ultrasound imaging system as well as a compact ultrasound system for neurostimulation to steer and focus the beam in a volume. In this paper, a sacrificial etching-based fabrication process for implementing a 16x16-element 2D CMUT array on a glass substrate with through-glass-interconnects is described in detail. Across the fabricated 256 elements of the 2D CMUT array, the mean resonant frequency is measured as 4.76 MHz with a standard deviation of 46.6 kHz. The fabricated 2D CMUT array shows a 100% element yield in fabrication and excellent uniformity in device performance. The process offers the advantages of developing 2D CMUT arrays on glass substrates that do not need to be compatible with anodic bonding.