Liu Yan, Cai Yao, Zhang Yi, Tovstopyat Alexander, Liu Sheng, Sun Chengliang
Institute of Technological Sciences, Wuhan University, Wuhan 430072, China.
Micromachines (Basel). 2020 Jun 28;11(7):630. doi: 10.3390/mi11070630.
With the rapid commercialization of fifth generation (5G) technology in the world, the market demand for radio frequency (RF) filters continues to grow. Acoustic wave technology has been attracting great attention as one of the effective solutions for achieving high-performance RF filter operations while offering low cost and small device size. Compared with surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators have more potential in fabricating high- quality RF filters because of their lower insertion loss and better selectivity in the middle and high frequency bands above 2.5 GHz. Here, we provide a comprehensive review about BAW resonator researches, including materials, structure designs, and characteristics. The basic principles and details of recently proposed BAW resonators are carefully investigated. The materials of poly-crystalline aluminum nitride (AlN), single crystal AlN, doped AlN, and electrode are also analyzed and compared. Common approaches to enhance the performance of BAW resonators, suppression of spurious mode, low temperature sensitivity, and tuning ability are introduced with discussions and suggestions for further improvement. Finally, by looking into the challenges of high frequency, wide bandwidth, miniaturization, and high power level, we provide clues to specific materials, structure designs, and RF integration technologies for BAW resonators.
随着第五代（5G）技术在全球的迅速商业化，对射频（RF）滤波器的市场需求持续增长。声波技术作为实现高性能射频滤波器运行同时提供低成本和小器件尺寸的有效解决方案之一，一直备受关注。与表面声波（SAW）谐振器相比，体声波（BAW）谐振器在制造高质量射频滤波器方面具有更大潜力，因为它们在2.5GHz以上的中高频段具有更低的插入损耗和更好的选择性。在此，我们对BAW谐振器的研究进行全面综述，包括材料、结构设计和特性。仔细研究了最近提出的BAW谐振器的基本原理和细节。还对多晶氮化铝（AlN）、单晶AlN、掺杂AlN和电极材料进行了分析和比较。介绍了提高BAW谐振器性能、抑制杂散模式、降低温度敏感性和调谐能力的常用方法，并进行了讨论和提出进一步改进的建议。最后，通过审视高频、宽带宽、小型化和高功率水平等挑战，我们为BAW谐振器的特定材料、结构设计和射频集成技术提供了线索。
