PREPARATION OF COMPOSITIONALLY GRADIENT AL-ALN FILMS BY RF REACTIVE SPUTTERING

The rf reactive sputtering of Al target in Ar+N2 mixed gas was applied to fabricate the compositionally gradient films consisting of Al and AlN phases. In this paper, two methods are presented to form the compositionally gradient Al-AlN films. The first is the N2 partial pressure-to-total pressure ratio (P(N2)/P(total)) control method, and the other is the rf power control method. The compositionally gradient Al-AIN films were deposited onto slide glasses, and the substrate temperature were room temperature and 200-degrees-C. The crystallographic structure, the composition and the morphology of deposited films were characterized by X-ray diffractometry, Auger electron spectroscopy and scanning electron microscopy, respectively. Both the P(N2)/P(total) and rf power control methods can be used to grow the compositionally gradient films. It is demonstrated that the deposited film has the structure with a c-axis perpendicular AlN layer on a non-oriented Al layer. The morphology of the films is greatly dependent on the substrate temperature, independently of the deposition method. It is also shown that the optical emission spectroscopy and the mass spectroscopy are useful tools to monitor the growth of these films.