基于近零质量负载石墨烯电极的超高频AlScN声表面波谐振器研究

Surface acoustic wave (SAW) devices are widely used in communications fields such as radar, electronic warfare, satellite communications and sensing field such as temperature, pressure and biosensors. With the development of high-frequency wireless communications industry as well as high-precision, lower-detection limit sensors, traditional SAW devices (below 3GHz) are no longer capable, and high-frequency SAW devices have become a trend. But super high frequency (SHF) SAW device research faces several difficulties: (1) in the SHF mode of operation, the electrode mass load effect is significant and the secondary effect brought by the traditional metal interdigital transducer (IDT) can not be ignored; (2) subjecting to process limits and metal properties, nm-level IDT preparation process has been had no major breakthrough; (3) high speed, adjustable AlScN piezoelectric film growth technology is still a challenge. For these three questions, the applicants propose a research on SHF AlScN surface acoustic wave resonators based on near-zero-mass loaded graphene electrodes. It is proposed to use near-zero-mass graphene as the interdigital electrode to solve the electrode mass load effect of high-frequency SAW Devices; as a result of using ultra-thin graphene interdigitated electrodes, nm-level width IDT preparation is possible; meanwhile, by exploring the growth mechanism of AlScN piezoelectric films, high-speed controlled deposition method is obtained to develop high-performance, ultra-high frequency SAW devices with center frequency higher than 20 GHz, promoting its development in the high-frequency wireless communications industries and high-precision, low-detection-limit sensor areas.

声表面波(SAW)器件在雷达、电子战、卫星等通信领域以及温度、压力等传感领域获得了广泛应用。随着高频通信以及高精度传感技术的发展，传统SAW器件(3GHz以下)已不能满足需求，高频SAW器件成为发展趋势。其研究面临几个难点：(1)超高频工作模式下，质量负载效应显著，传统的金属叉指换能器(IDT)带来二次效应不可忽略；(2)受工艺限制和金属特性的影响，纳米尺度IDT制备工艺一直没有大的突破；(3)高速可调的AlScN压电薄膜生长技术仍然是个挑战。针对这三个问题，申请人提出基于近零质量负载石墨烯电极的超高频AlScN SAW谐振器研究。拟采用近零质量的石墨烯IDT解决超高频下电极质量负载效应的影响；由于采用超薄石墨烯，纳米尺度IDT制备成为可能；摸索AlScN压电薄膜的生长机理，获得高速可控沉积方法，开发超高频SAW器件(20 GHz)，推动其在高频无线通信以及高精度、低检测下限传感的应用。

项目背景：声表面波（SAW）器件具有信号处理简单方便、抗辐射功能强、动态范围大等优点广泛应用于移动通信系统、电视、军用雷达、传感器、滤波器中。压电材料和叉指电极是决定其性能的关键要素。氮化铝薄膜具有高声速和温度稳定性好等优点，是制备声表面波器件的理想材料；但其有效可靠制备仍是难题，石墨烯具有优异的力学性能和电学性能，质量轻，厚度薄，有望减小声表面波质量负载效应、制作纳米级叉指电极，但尚未有实验论证，申请人提出基于石墨烯电极和压电薄膜AlN的声表面波器件研究。.主要研究内容：项目主要围绕新型结构SAW器件理论建模、加工工艺进行研究，研究内容包括：理论分析不同类型、厚度电极对SAW器件性能的影响，压电薄膜的成膜机理和制备工艺，石墨烯的大面积制备工艺和转移工艺，基于石墨烯和氮化铝多层膜结构的SAW器件的制备方法和性能检测以及其初步应用。.重要结果：研究了多层膜结构SAW器件的耦合模型和P-矩阵表示方法，实现了多层膜SAW器件的模拟，对不同衬底材料、叉指电极厚度等对声表面波器件的影响规律进行了仿真分析，判定了波模型；获得了氮化铝薄膜在蓝宝石、碳化硅、金刚石/单晶硅等高声速衬底材料上的制备方法，表面粗糙度最低可达1.06nm。获得了高c轴取向(002)，高表面平整度，低应力的压电薄膜；掌握了石墨烯叉指电极的转移、光刻、刻蚀等工艺，实现了不同衬底材料和不同叉指电极材料的声表面波器件制备；对金电极/铌酸锂、金电极/氮化铝/蓝宝石、石墨烯电极/铌酸锂、石墨烯电极/氮化铝/蓝宝石、石墨烯电极/氮化铝/碳化硅等声表面波器件进行了测试，均获得了良好的声表面波信号，频率为300MHz左右，获得了SAW器件的可靠、稳定的制备方法。并基于制备的声表面波器件实现了声表面波器件对TNT检测的应用探索，初步获得了0.1%的灵敏度。.关键数据：项目完成预期目标，发表论文7篇，其中第一作者和通讯作者4篇，2篇会议论文为MEMS会议。另有1篇专著在修改，1篇EI论文已录用。申请国家发明专利1项，培养了研究生1名。.科学意义：项目首次提出采用和实现了石墨烯作为叉指电极，理论、仿真和实验验证了电极质量负载效应对SAW器件影响；解决了压电薄膜相关理论和加工问题，完成了基于石墨烯和压电薄膜SAW器件的自主制备，为下一步高性能高频声表面波器件的研究提供了有力支撑。