A self-aligned mask-free fabrication process for high-frequency ZnO array transducer

High-frequency ultrasonic array transducers are essential for high resolution imaging in clinical analysis and Non Destructive Evaluation (NDE). However, the fabrication of piezoelectric array transducers is a great challenge due to the small features in elaborating piezoelectric array films. This paper describes a MEMS based self-aligned mask-free process for fabrication of ZnO linear array transducers of more than 100MHz. A four-step-rotation deposition approach is proposed and investigated, that improves the lateral growth in ZnO array deposition. The ratio of vertical to lateral growth is improved by 40% compared to one-step deposition method. The results prove that the reduction of the lateral growth helps to achieve full-kerfed ZnO array with smaller pitch.