Progress towards wafer-scale fabrication of ultrasound arrays for real-time high-resolution biomedical imaging

Purpose – High-frequency transducer arrays that can operate at frequencies above 30?MHz are needed for high-resolution medical ultrasound imaging. The fabrication of such devices is challenging not only because of the fine-scale piezocomposite fabrication typically required but also because of the small size of arrays and their interconnects. The purpose of this paper is to present an overview of research to develop solutions for several of the major problems in high-frequency ultrasound array fabrication. Design/methodology/approach – Net-shape 1-3 piezocomposites operating above 40?MHz are developed. High-quality surface finishing makes photolithographic patterning of the array electrodes on these fine scale piezocomposites possible, thus establishing a fabrication methodology for high-frequency kerfless ultrasound arrays. Findings – Structured processes are developed and prototype components are made with them, demonstrating the viability of the selected fabrication approach. A 20-element array operating at 30?MHz is patterned and characterised. Furthermore, an electrode pattern suitable for a 20-element array operating at 100?MHz is created to demonstrate the state of the art of photolithography processing directly on piezocomposite. Practical implications – The work reported suggests that ultrasound arrays for real-time biomedical imaging will be viable at higher frequencies than presently available commercially or previously reported in the research literature. Originality/value – The main elements of a novel, fully mask-based process for high-frequency ultrasound transducer array fabrication are presented in outline in this paper