Impact of nitrogen concentration on the growth of h-AlN thin films using RF-magnetron sputtering for microwave applications

This study is of significant importance as it investigates the impact of argon to nitrogen gas ratio on the electrical and dielectric properties of AlN thin films deposited using RF magnetron sputtering. The AlN thin films’ X-ray diffraction (XRD) pattern revealed a hexagonal structure and is complemented by Raman spectroscopy. XPS high-resolution spectra reveal Al-N ∼ 74.32 eV with 83.66 % and N-Al-O ∼ 398.4 eV with 58.52 % for the h-AlN thin film deposited with 25 % nitrogen. The optical bandgap of ∼6.07 eV with a refractive index of ∼2.1 is obtained. The average RMS roughness achieved is ∼0.7 nm. The lowest leakage current density achieved is (3.06 $\times$ 10⁻⁵ A/cm²). The optimal dielectric properties attained at microwave frequencies include ${\epsilon }_r=$ 8.865, and $\tan \delta$ $=$ 4.143 $\times {10}^{-3}$ at 10 GHz. Thus, the obtained AlN thin films with the optimal conditions are well suited for microwave and high-frequency applications.