Spectral analysis of AlN annealed at elevated temperatures

Abstract

The characteristics of aluminum nitride (AlN) thin films subjected to post-deposition annealing at different temperatures were investigated in this study. AlN thin films were grown on various substrates without heating via reactive radio frequency (RF) magnetron sputtering at 50 W. The samples were then annealed in a nitrogen atmosphere at varying temperatures in order to improve the crystallinity of the thin films. The resulting films were characterized using x-ray diffraction (XRD), x-ray fluorescence (XRF), resistance tests, Raman spectroscopy and optical imaging. 2θ/ω XRD scans of the films revealed that the sputtered films were amorphous even after post-deposition annealing. XRF confirmed the presence of Al in the films, and resistance testing ruled out the possibility of the sputtered film being metallic Al. Raman microscopy did not identify any characteristic peaks, but found out that annealing improved the scattering properties of the film. Optical images of the films revealed the consolidation of cavities proportional to the annealing temperature. To summarize, the study found out that deposition at low power and high pressure yielded amorphous AlN films, and that annealing enabled the migration of cavities in the film but did not promote the formation of crystal structures in the film.