Influence of N2/Ar-flow ratio on crystal quality and electrical properties of ScAlN thin film prepared by DC reactive magnetron sputtering

Scandium aluminum nitride alloy (ScAlN) thin films were prepared using DC reactive magnetron sputtering with a scandium aluminum alloy (Sc0.06Al0.94) target on n-type silicon substrates. We have investigated the influence of N2/Ar-flow ratio on the crystalline structure, the surface morphology and the electrical properties of ScAlN thin films. Consequently, it was statistically proved that the N2/Ar-flow ratio was an important control factor in the process of sputtering. According to the peak intensities in θ/2θ scans and rocking curve FWHM measurements of the (0 0 2) peaks, the crystalline quality of ScAlN thin film first increased and then decreased, reaching the best crystalline state at a N2/Ar-flow ratio of 3.3:7. The best surface morphology of ScAlN thin film was obtained at N2/Ar-flow ratios of 3.2:7, 3.3:7 and 3.4:7 and the surface roughness reached a minimum of 2.612 nm at 3.3:7. The resistivity and dielectric constant first increased to maximum values of 3.35 × 1012 Ω cm and 13.6, and then decreased with the ratio increasing. Moreover, ScAlN thin film exhibited a higher value of resistivity and dielectric constant when compared with un-doped AlN thin film. In addition, when the N2/Ar-flow ratio was 3.3:7, the highest breakdown field strength and lowest leakage current were obtained, with values 1.12 MV/cm and 3 × 10−8 A, respectively.