Residual stress of AlN films RF sputter deposited on Si(111) substrate

AlN films with (002) crystal orientation are widely used in various resonator-based applications. Low intrinsic stress is one of the important requirements for the thin film stacks employed in electroacoustic devices. In this paper, AlN films were deposited by reactive radio frequency (RF) sputtering with various conditions. The effects of N2 concentrations, sputtering pressure, substrate temperature, and RF power on the microstructure and stress of AlN films were investigated. The X-ray diffraction, atomic force microscopy, and field emission scanning electron microscopy were utilized to investigate the orientation and surface morphology of AlN films. A systematic study of the stress of AlN was done as a function of the deposition parameters. As the nitrogen concentration decreased, the sputtering pressure increased. The residual stress has a change tendency from compressive to tensile. The substrate temperature and RF power affect stress slightly. The N2 concentrations is the major fact that influences on stress of sputtering AlN films.