High-SPL and Low-Driving-Voltage pMUTs by Sputtered Potassium Sodium Niobate
Fan Xia, Yande Peng, Sedat Pala, Ryuichi Arakawa, Wei Yue, Pei-Chi Tsao, Chunming Chen, Hanxiao Liu, Megan Teng, Jong Ha Park, Liwei Lin
Abstract
This work presents an air-coupled piezoelectric micromachined ultrasonic transducer (pMUT) with high transmitting acoustic pressure by using sputtered potassium sodium niobate (K,Na)NbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (KNN) thin film with a high piezoelectric coefficient (e <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</inf> ~ 8-10 C/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and low dielectric constant (ϵ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> ~ 260-300) for the first time. The fabricated KNN pMUT with a resonant frequency at 104.5 kHz has been tested to exhibit unprecedented results: (1) high sound pressure level (SPL) of 109 dB/V at a distance of 10 cm, which is 8 times higher than that of AlN-based pMUTs at a similar frequency; (2) low-voltage operation of only 4 volts peak-to-peak amplitude (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-p</inf> ); and (3) good receiving sensitivity. As such, this work presents a new class of high-SPL and low-driving-voltage pMUTs for potential applications in various fields, including consumer electronics, such as but not limited to haptic feedback, loudspeaker, and AR/VR systems.