Effects of growth temperature and reactor pressure on AlN thin film grown by metal-organic chemical vapor deposition

Following the development of the semiconductor industry, advanced and multifunctional material aluminum nitride (AlN) is widely used. However, AlN thin film faces the dilemma of low crystal quality or cracking in practical applications. This paper presents a high crystal quality and crack-free AlN thin film with a thickness of over 510 nm grown on a sapphire substrate by metal-organic chemical vapor deposition (MOCVD). We have analyzed the thin film deposition mechanism of the MOCVD reaction system using different growth temperatures and reactor pressures and optimized the growth mode of AlN thin film. Wherein the growth temperature refers to the substrate temperature while the film is deposited. It was shown that the deposition rate of the AlN thin film is significantly affected by the reactor pressure. As shown by the x-ray diffraction patterns, the AlN thin films exhibit a (002) preferred orientation while non-(002) reflections are extremely weak. At constant pressure, the intensity of the diffraction peak of (002) orientation increased with the growth temperature. Furthermore, the surface morphology observed by atomic force microscopy revealed a decrease in the surface roughness with increasing growth temperature. The AlN thin film grown at a growth temperature of 1300 celcius under 10,000 Pa exhibited better (002) orientation in this work. The full width at half maximum of its rocking curve was 0.033 degrees for (002) planes. Beside, the sample showed a flat and dense surface with a root-mean-square surface roughness of 8.4 nm. This study offers an improvement in the deposition of AlN thin films, promising for AlN-based devices operated in various conditions.