ZnO薄膜生长及声表面波性能研究

Growth of ZnO thin film and its surface acoustic wave properties

采用传统射频磁控溅射技术,通过引入Si O2缓冲层以及调节工作气压的方法,在Si衬底上制备具有高度(1120)择优取向的Zn O薄膜.采用X射线衍射技术和原子力显微镜分析Zn O薄膜的晶体特性和择优取向.研究发现,引入Si O2缓冲层能显著减小Zn O/Si O2/Si三层结构声表面波器件的温度延迟系数(temperature coefficient of delay,TCD),当Si O2缓冲层厚度为200 nm时,Zn O薄膜同时具有(0002)和(1120)择优取向,且TCD值仅为2×10-6℃-1左右,说明器件温度稳定性佳.当工作气压降低时,Zn O(1120)择优取向增强,相应的声表面波器件的机电耦合系数(K2)也增大.在大机电耦合系数和高温度稳定性的Zn O/Si O2/Si三层结构的基础上,有望制作出高性能的Love波声表面波生物传感器.

Using a conventional radio frequency（ RF） magnetron sputtering system, we have succeeded in fabricating ZnO films with high （1120） preferred orientation on Si substrate by introducing a SiO2 buffer layer and adjusting the sputtering gas pressure. The crystallographic characteristics and the preferred orientation of ZnO films were characterized by X-ray diffraction （ XRD） and atomic force microscopic （ AFM） analysis. The temperature coefficient of delay （ TCD） of the ZnO/SiO2/Si SAW device decreases significantly when a SiO2 buffer layer is introduced. When the thickness of SiO2 buffer layer is 200 nm, ZnO film shows （ 0002 ） and （ 1120 ） preferred orientations simultaneously, and the TCD of ZnO/SiO2/Si SAW device is nearly 2 × 10 ^-6℃^ -1 , indicating that the device main-tains good temperature stability. When the sputtering gas pressure decreases, the （ 1120 ） preferred orientation is enhanced, and the corresponding electromechanical coupling coefficient （ K^2 ） of the SAW devices enlarges. The tri-layer structure of ZnO/SiO2/Si with large K^2 and high temperature stability is promising for fabricating high performance Love mode SAW biosensors.