ZnO压电薄膜的制备及基于薄膜结构的声表面波传感器的研究

In this project, we present the deposition of ZnO piezoelectric films on piezoelectric substrates (quartz, LiNbO3, LiTaO3) or non-piezoelectric substrates (Si, SiO2, sapphire), by which the fabrication and the real-time sensing measurement of the surface acoustic wave(SAW) sensors based on the films are carried out. The piezoelectric ZnO films with good crystalline qualities are deposited by magnetron sputtering and/or metal oxidation chemical vapor deposition (MOCVD). The deposition methods and parameters of the ZnO piezoelectric films with different orientations on the nonepitixial substrates are optimized. In order to improve the stability of the SAW sensors, IDT with new structures and dual differential amplification circuit are designed and fabricated. The sensitivity of the sensors can be improved by the piezoelectric substrates due to the high electromechanical coupling coefficients. The non-piezoelectric substrates are favour for the compatibility and integration of the SAW sensors with other integrated circuits. Meanwhile, the acoustic characteristics of the SAW sensors with multi-layered structures are theoretically analyzed to optimize the thicknesses of the ZnO piezoelectric films, the materials and thicknesses of the guiding layers, as well as the position of the IDT. The SAW sensors are fabricated according to the theoretical results and the sensing measurements are also carried out.The results can provide a predictable and theoretical basis for further application of SAW devices.

本项目主要为压电（石英，铌酸锂，钽酸锂）或非压电基底(硅, 光学玻璃, 蓝宝石等)上ZnO压电薄膜的制备及基于薄膜结构的声表面波（SAW）传感器的研制和实时传感测试研究。利用磁控溅射技术、金属氧化物化学气相沉积技术等，优化非外延生长基底上高质量的，不同晶体取向的ZnO压电薄膜的制备方法和参数，结合半导体平面工艺设计新型结构IDT以及双路差分放大电路提高SAW传感器的稳定性。利用压电基底的高机电耦合系数改善SAW传感器的传感灵敏度；非压电基底实现SAW传感器与其他电子电路的兼容集成。同时，建立多层结构SAW传感器的计算模型，对SAW传感器的声学特性予以理论计算分析，得到最佳的ZnO压电薄膜的厚度，导波层材料及其厚度以及IDT电极的位置等结构参数。根据理论分析结果研制基于压电薄膜的SAW传感器并进行实时传感测试。

本项目主要研究压电基底（铌酸锂，钽酸锂）和非压电基底 (光学玻璃, 蓝宝石等) 上ZnO 压电薄膜的制备及基于薄膜结构的声表面波（SAW）传感器的研制和实时传感测试研究。目前，基于(110) ZnO压电薄膜的SAW传感器的研究较少，利用(110) ZnO压电薄膜/非压电基底结构激发SAW，研制SAW湿度传感器的相关结果尚未有报道。我们利用RF磁控溅射技术，制备高质量的(110) ZnO 压电薄膜于R-蓝宝石基底，成功激发SAW（Love波和Rayleigh波），研制新型结构的SAW湿度传感器，并进行湿度的实时传感测试，检测结果显示，Love波传感器具有更高的灵敏度，性能更优化。同时，利用有限元方法，建立多层结构SAW 传感器的计算模型，理论研究了(110) ZnO压电薄膜/非压电基底（光学玻璃, R-蓝宝石）结构SAW传感器的声学特性，讨论了色散曲线、机电耦合系数，质量灵敏度以及声波传播方向对声波特性的影响等，为实验研究提供了理论基础。. 另一方面的工作，采用RF磁控溅射法结合水热合成法制备ZnO纳米材料，利用其大的表面体积比等特点，将ZnO纳米材料作为气体敏感膜，分别沉积于128°YX-LiNbO3和36°YX-LiTaO3基片，研制多层结构的声表面波（Rayleigh波和Love波）氢气传感器，并进行室温条件下氢气的实时传感检测，结果显示，与Rayleigh波传感器比较，Love波H2传感器的灵敏度更高，而且低浓度范围H2的传感效果更明显。由于Love波没有垂直于表面的位移分量，因此，所研制的Love波传感器可以用于液体环境的传感检测。