Influence of coating thickness on the microstructure, composition and optical properties of aluminum nitride thin films grown on silicon substrates via low-temperature PEALD

Within the framework of the study, fine-grained nanocrystalline aluminum nitride films were obtained using the PEALD method at the temperature of 250 °С and the number of deposition cycles from 80 to 500 on single-crystal silicon substrates. Low-temperature synthesis processes were carried out in the self-limited growth regime of the PEALD method at the constant growth rate of ∼0.115 nm/cycle. The obtained samples were studied by ellipsometry, FTIR-spectroscopy, X-ray diffraction analysis, Auger spectroscopy, Scanning electron and Atomic force microscopy. It was found that the samples in the IR-absorption spectra and ω/2θ-scans had bands and reflections characteristic for wurtzite AlN with hexagonal structure. It was shown that an increase in the coating thickness led to an increase in the crystallinity and optical density of the film material, the crystallites size, and values of the root-mean-square (RMS) roughness. In this case, significant changes in the crystal lattice parameter and relaxation of internal mechanical stresses within the obtained values of the AlN layers thicknesses were not observed.