Influence of sputtering power on crystal quality and electrical properties of Sc-doped AlN film prepared by DC magnetron sputtering

Scandium-doped aluminum nitride alloy (ScAlN) thin films were deposited on (1 0 0) silicon substrates by DC reactive magnetron sputtering method using a scandium aluminum alloy (Sc0.06Al0.94) target. The influence of sputtering power on the crystalline structure, surface morphology and electrical properties of ScAlN thin films were investigated. The XRD patterns indicated all the films showed a single pronounced hexagonal (0 0 2) peak. 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 sputtering power of 130 W. The best surface morphology of ScAlN thin film was obtained at 130 W and the surface roughness reached a minimum of 2.612 nm. Then the piezoelectric response of ScAlN thin films was measured and the highest value, 8.9 pC/N, was achieved at the sample with the best crystal quality. The resistivity and dielectric constant change in the same rule as the crystal quality, first increasing to a maximum value of 3.35 × 1012 Ω cm and 13.6, and then decreasing with the sputtering power increasing. In addition, when the sputtering power was 130 W, the highest breakdown field strength and lowest leakage current were obtained, with values 1.12 MV/cm and 3 × 10−8 A, respectively.