Preparation of AlN Thin Film Deposited on SiO<sub>2</sub> for Improving Temperature Frequency Coefficient of FBAR Used in CSACs

Abstract

AlN films were deposited by RF magnetron sputtering on the SiO2 films with different thickness. Preferred orientation, grain size, surface roughness and grain growth of the AlN films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and field-emission scanning electron microscopy (FESEM). It's found that when the thickness of SiO2 films are 100 nm and 200 nm, the AlN films have characteristics of good C-axis preferred orientation, good surface roughness and vertical grain growth, which are suitable for application in thin film bulk acoustic wave resonators (FBARs). When the thickness of SiO2 film is 300 nm, although the AlN film has characteristics of good C-axis preferred orientation and surface roughness, the grain growth is tilted, which is not suitable for application in the FBARs.