A Piezoelectric Micromachined Ultrasonic Transducer Using Thin-Film Lithium Niobate

Abstract

This letter presents the first piezoelectric micromachined ultrasonic transducer (PMUT) based on thin-film lithium niobate (LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ). The figures of merit (FoMs) of LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> as ultrasound sensors and transducers are first studied, showing great prospective as a balanced transceiver platform. Efficient flexural mode excitation is achieved using a proposed lateral-field-excitation (LFE) structure. The implemented device shows a flexural mode at 7.6 MHz, with a high electromechanical coupling (k <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) of 4.2%. Measured quality factor ( Q) in vacuum is 2605, indicating the low structural loss, while measured Q in air is 264, suggesting the ultrasound radiation. A dynamic displacement sensitivity of 20.2 nm/V is measured. Upon further optimizations, LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -based PMUTs are promising candidates for miniature ultrasound applications.