Caractérisation des textures de films AlN

Abstract

The objective of this thesis is to study the influence of anisotropy on the quality of AlN thin films, developed by two physical vapor deposition (PVD) techniques, DCMS and HiPIMS. AlN exists in two phases: a stable hexagonal phase and a cubic one generally considered as metastable. We are interested particularly in highlighting the last mentioned phase. For this, we have analyzed the texture of several series of AlN films deposited on different substrates of different nature and orientations by X-ray diffraction (XRD). The hexagonal phase is present under the form of fiber (0001), with reinforcements more or less remarkable, when the film is deposited on Si substrate of orientations (100) and (111). It is important to mention that the fiber (0001) can be tilted with respect to the normal of the substrate, mainly when the thickness increases. The use of SiC-6H substrate with lattice agreement with AlN, makes epitaxial growth possible at a temperature from 200 to 250 °C. Following the diffracted intensity has shown the absence of epitaxial growth of AlN (PVD), at low temperatures, on a composite substrate of AlN Kyma/Si (111). Furthermore, the use of AlN buffer layer, 2 nm thick, developed at high temperatures, makes the epitaxial growth of AlN (PVD) possible on Si (111) and at low temperatures. The XRD texture analysis allowed, as well, the highlighting of the AlN cubic phase. This cubic phase was carefully studied especially when it is not much mentioned in literature. We have shown that it is a transition layer between hAlN transition and the Si (100) substrate. The AlN cubic phase shows a crystalline response with several orientations for two methods, DCMS and HiPIMS, with a higher intensity in the case of DCMS. The lattice mismatch between the different structures and orientations confirm that the growth of hexagonal AlN under the form of (0001) fiber is facilitated by the presence of this AlN cubic phase.