Microstructures diagram of magnetron sputtered AlN deposits: Amorphous and nanostructured films

To synthesise homogeneous nanostructured aluminium nitride deposits on [0 0 1] Si substrates, the radio frequency magnetron reactive sputtering deposition process was tested. The microstructure and chemical composition of the films were studied as a function of the plasma working pressure P and the radio frequency power W. This paper describes the different morphologies that could be produced. Four microstructural types were identified and are presented versus the two parameters P and W as a map of microstructures. The first one is the well-known columnar microstructure. The second one is made of short rods. The third one consists of equiaxed particles while the fourth and last microstructure is amorphous. The “deposit morphology–process parameters” correlation is discussed. The progressive evolution of the microstructures could be related to the deposition rate of the films. Morphology was studied by transmission electron microscopy, and chemical investigations were performed by energy dispersive X-ray spectroscopy and Auger electron spectroscopy.