Gas Pressure Dependence of AlN Film Properties in Alternating Sputtering System

AlN films were prepared in N2 and N2/Ar gas by the alternating DC sputtering method wherein two Al targets facing each other were sputtered alternately, and the mechanism of film damage in AlN film preparation was investigated. When the gas pressure was lower than 3 mTorr, the crystalline orientation of the film inclined slightly toward the direction of incidence of depositing atoms. In this system, the influence of plasma exposure on the film properties was decreased. This was due to the decrease of electron flow into the substrate. Degradation of the c-axis orientation was ascribed to both the tilt of the growth direction of the (00·2) plane at low gas pressures and film bombardment by positive ions with energies above 60 eV.