靶基距对反应溅射AlN薄膜微结构和性能的影响

采用射频(RF)磁控反应溅射法在Si基底上制备了氮化铝(AlN)薄膜,利用X射线衍射(XRD)、傅立叶红外光谱(FTIR)、扫描电子显微镜(SEM)和纳米力学测试系统研究靶基距对AlN薄膜取向性、微结构、形貌和力学性能的影响。结果表明,靶基距较大时,形成的AlN薄膜为非晶态,薄膜表面较疏松;随着靶基距的减少,AlN薄膜变为多晶态,且具有(100)择优取向;随着靶基距的进一步减少,薄膜结晶质量变好,晶粒变大,薄膜变得更致密,择优取向也由(100)逐渐向(002)转变;靶基距较小时,AlN压电薄膜与基底结合得更牢固,而压电薄膜与基底结合的紧密程度对多层膜声表面波(SAW)器件性能优劣的影响至关重要。

Effect of target-substrate distance on the microstructure and properties of AlN film

AlN films were deposited on Si substrates using radio frequency(RF) magnetron sputtering.The orientation,microstructure,morphology and mechanical properties of the films were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FTIR) and nanoindention.The results show that the deposited AlN films are transformed from non-crystalline to polycrystalline and the crystal quality is improved with the decrease of the substrate-target distance.Meanwhile,the surface of the films becomes more compact and the size of the grains becomes larger as the substrate-target decreases.For polycrystalline AlN films,a longer substrate-target distance is beneficial for the growth of the(100) and(110) planes,while a shorter distance is conducive to the formation of the(002) plane.The preferential orientation of the AlN thin films is also explained from the viewpoint of the mean free path of sputtered particles and the Al-N band(B1 band and B2 band).Moreover,good adhesion of the AlN piezoelectric film to the substrate,which is critical for the performance of the surface acoustic wave(SAW) devices,can be obtained with shorter target-substrate distance.