Filtered arc deposition and implantation of aluminium nitride

The formation and properties of AlN thin films deposited on Si and sapphire substrates were studied. A cathodic aluminium arc in nitrogen gas was used at room temperature to prepare the samples. Additionally, high voltage pulses between 0 and –10 kV with a duty cycle of 9% were applied to the substrate. Without filtering only condensed aluminium droplets were observed on the substrates while transparent films with very few droplets were produced when a filter was used to reduce the number of macroparticles. Growth rates of some 20 nm/min of pure AlN were determined with Rutherford backscattering spectroscopy. X-Ray diffraction measurements were employed to determine the crystal quality. Highly textured hexagonal AlN films with the c-axis oriented normal to the surface were found at all conditions, from no additional bias to 10 kV pulses. The surface roughness remained low over the whole voltage range with values between 0.3 nm without bias and a maximum of 5 nm at 5–7.5 kV. A rather high refractive index in the visible region was found with spectroscopic ellipsometry.