A Novel Method for Fabrication of High-Frequency (>100 MHz) ZnO Ultrasonic Array Transducers on Silicon Substrates

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 an array. A novel technique is presented 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-mu m-pitch ZnO sandwich array is achieved with a thickness of 8 mu m for 300 MHz. Finite element method is employed to simulate the wave propagation in water based on this new transducer configuration. The acoustic field results indicate this configuration has an acceptable performance. A potential application is proposed based on integration with microfluidics.