Design strategy and micromachining technology of AT-cut high-frequency quartz resonators: A review

Abstract

Quartz resonators have received attention in communication, timing, and consumer electronics to generate stable signals for reliable data transmission. With the rise of 5G communication, there is an increasing demand for miniaturized quartz resonators with high frequencies. AT-cut quartz crystals are ideal materials for high-frequency quartz resonators due to their excellent frequency stability and low-temperature coefficient. Due to the processing limitations of mechanically thinned AT-cut quartz wafers, the quartz micromachining technology is developed to achieve precise and complex microstructure manipulation. This review begins by discussing the working principles of AT-cut quartz resonators and explores the impacts of mass loading and energy trapping on their electrical performance. Based on these theoretical foundations, this review categorizes various fundamental frequency vibration AT-cut quartz resonator structures including planar, mesa, inverted-mesa, and bi-mesa, and compares their performance metrics. Furthermore, to achieve the above structures, this review outlines the advantages and limitations of different micromachining technologies, including machining, wet etching, deep reactive ion etching, laser micromachining, abrasive jet machining, and electrochemical diacharge maching technologies. Finally, this review addresses the challenges in structural design and highlights innovations in micromachining technologies. By exploring design strategy and micromachining technology, this review aims to provide insights and future directions for AT-cut quartz resonators, focusing on achieving higher frequencies, smaller sizes, and enhanced reliability.