Ion beam synthesis of aluminium nitride: Characterisation of thin AlN layers formed in microelectronics aluminium

Buried AIN thin layers have been formed by high nose N+ ion implantation into microelectronics grade Al films (containing 1 at.-%Si), which were deposited on Si wafers. The structures obtained have been characterised by spreading resistance measurements, transmission electron microscopy, secondary ion mass spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. The results show the formation of buried dielectric precipitates of crystalline AIN at implantation doses below the threshold and a continuous polycrystalline AIN layer at doses above the threshold. The AIN grains have the wartzute structure, sizes of about 10-15 nm, and a preferred orientation in relation to the Al matrix, namely, [110](AIN) parallel to [110](Al). The data also show that, under certain conditions, the main impurities (Si and O) are gettered in the buried layer. Moreover; for thin Al films, the formation of a Si rich surface layer is observed. This surface layer is formed by Si diffusion from the substrate, probably due to the penetration of N+ ions into the Si substrate. The distribution and evolution of these impurities and the different phases formed are studied as a function of the thickness and grain size of the Al film, as well as of the annealing processes. (C) 1995 The Institute of Materials.