STUDY OF THE OXIDATION OF ALUMINUM NITRIDE COATINGS AT HIGH-TEMPERATURE

Thin films of aluminium nitride have been deposited on silicon or alumina substrates by plasma enhanced chemical vapour deposition. The oxidation behavior of these coatings is studied and compared with the behavior of aluminium nitride thick films. We have analyzed the evolution of their optical properties at high temperature by laser spectrophotometry. The complementary characterization methods were high temperature X-ray diffractometry, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses. The oxidation of these coatings involves the formation of a solid solution of oxygen in the aluminium nitride in excess of 25 at.% up to a temperature of 900 degrees C, then of a biphasic AlN solid solution + alumina-alpha until the complete transformation into alpha-alumina at 1200 degrees C. The methods we have used underline a supplementary phenomenon of interaction with the substrate in the case of thin films on silicon. The results obtained led to a coherent presentation of the behavior of this material under oxidation.