A novel method to fabricate full-kerfed highfrequency (>100 MHz) ultrasonic array transducers

High-frequency ultrasonic transducer arrays are essential for efficient imaging in clinical analysis and nondestructive evaluation (NDE). However, the fabrication of piezoelectric transducers is really a great challenge due to the small features in piezoelectric films. This paper describes a novel technique to fabricate thick-film ZnO ultrasonic array transducers. Piezoelectric elements are formed by sputtering thick-film ZnO onto etched features of a silicon substrate so that the difficult etching process for ZnO films is avoided by etching silicon. This process is simple and efficient. A 13-μm-pitch ZnO sandwich array is achieved with a thickness of 8 μm for 300 MHz. Finite element method is employed to calculate its electrical properties, including electrical impedance and crosstalk. The array is characterized by a network analyzer. The measured results are in good agreement with the theoretical predictions.