Influence of deposition conditions on optical properties of aluminum nitride (AN) thin films prepared by DC-reactive magnetron sputtering

Aluminum nitride (AlN) films have been prepared by DC-reactive magnetron sputtering technique. The optical properties of the films have been studied by optical spectroscopy with an incoherent light source. For the first time, it is demonstrated that for certain deposition conditions, the film may behave as a metallic thin film. In this case, there are strongly enhanced reflection peaks in the optical spectrum and the peaks may red-shift according to the degree of the metallization. The microscopic structures of the films have also been studied with scanning electron microscopy (SEM) and X-ray diffraction (XRD). It turns out that the orientation of the crystallites in the film determines whether the film remains dielectric or becomes metallic. It is found that the degree of the metallization depends on the proportion of (1000) preferred orientation in the film. In the deposition process, various deposition parameters have been experimented and a close relation between the deposition parameters and the status of the films is established. The most influential deposition conditions are as follows: the substrate temperature in a range from 200 to 700 degreesC, the gas composition ratio of Ar/N-2 from 20/80 to 60/40 and the plasma current from 0.2 to 0.45 A. (C) 2002 Elsevier Science B.V. All rights reserved.