DC sputtering of highly c-axis AlN films on top of 3C-SiC (111)-on-Si (111) substrates under various N2 concentrations

Abstract

This article reports on the direct current sputtering of AlN thin films on top of a cubic-silicon carbide (111) on silicon (111) substrates. The authors varied the nitrogen (N2) concentrations, while keeping other process parameters fixed at the power of 1200 W, the substrate temperature of 350 °C, the target to substrate distance of 20 cm, and the sputtering pressure of 2 mT. The total N2/Ar gas flow is 50 sccm, and the poison mode starts at 40%. The x-ray diffraction results show that the AlN films are highly oriented along the (002) orientation at various N2 concentrations. The values of the three parameters support this observation, namely, (1) the extracted full width at half maximum (FWHM) of (002) diffraction peaks with the median of 0.28° and the standard deviation of 0.012°, (2) the area of AlN (002) under the curve is between 92% and 97%, and (3) the grain sizes are between 30.11 and 32.3 nm. The omega scan rocking curve of two samples at 40% and 80% N2 concentrations depicts good quality AlN (002) films with the FWHM values of 1.5° and 2°, respectively. The relationship between the N2 concentrations and the film's properties is elucidated. Finally, the authors discuss the effect of the lattice mismatch of 1% between AlN (002) and 3C-SiC (111).