A strong dependence of sputtering power on c-axis oriented aluminium nitride on Si (111): A structural and electrical study

Growing and controlling the c-axis orientation of the aluminium nitride (AlN) thin film on unheated Si (111) substrates using reactive magnetron sputtering are challenging. Sputtering parameters such as nitrogen concentration and sputtering power were effectively tuned to grow the c-axis oriented AlN thin film. The results show that a low concentration of (25%) N₂ is enough for forming AlN at a reduced flow rate, whereas a higher flow rate requires a higher concentration of N₂. Low concentration with a low flow rate is preferred to grow AlN at low temperature and power. The poor crystallinity of AlN with (100) orientation was improved by varying the power from 75 to 175 W. The X-ray diffraction results confirmed the improvisation of crystallinity of grown AlN films and indicated the strong dependence of preferred c-axis orientation on sputtering power. Also, the dependence of sputtering power on microstrain and stress was analysed. The surface morphology study by field emission scanning electron microscopy and topography measured by an atomic force microscope shows a dependence on sputtering power. The high c-axis orientation was observed at 175 W with low surface roughness, low leakage current density (2 × 10⁻⁹ A/cm²) and low dielectric constant (6.8).