Correlation between the oxygen content and the morphology of AlN films grown by r.f. magnetron sputtering

To understand the influence of the oxygen on the crystallography of AlN thin films made by physical vapour deposition r.f. magnetron, three different oxygen content AlN films were prepared at room temperature for two values of the energy of the species building the film (low energy obtained by using: low power W, high pressure P; high energy obtained by using: high W, low P). It is observed that the crystalline morphology of the films not only depends on the process parameters (W and P), but is also particularly related to the oxygen content in the films. Regardless of P and W used here, low oxygen content films (5 at%) are columnar. The increase in oxygen content (15–30 at%) reduces the grain size without creating phases like Al2O3 or AlNO, and very rich oxygen films (50 at%) are amorphous. From this study, assumptions are made for the localization of oxygen atoms in the AlN phase.