Structure and morphology evolution of ALN films grown by DC sputtering

Aluminium nitride (AlN) films have been deposited on (100) oriented silicon substrates by dc reactive magnetron sputtering for different deposition times (10≤t≤200 min) at a constant growth rate of 5 nm/min. The films have been characterized by tapping mode atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques in order to study the correlation between the film growth and structural properties. The film growth has been characterized through the analysis of the temporal evolution of surface roughness, σ, obtained from the AFM data. The XRD measurements have shown the presence of a polycrystalline hexagonal phase for all film thicknesses. For t<40 min, the films are composed of (002) textured regions embedded in a less ordered matrix. In this regime, the steep change of σ with the deposition time as σ∝t is consistent with an unstable growth mode. In contrast, for 40≤t≤200 min, a homogeneous structure with hexagonal (002) texture is mainly present, and the film roughening considerably decreases to σ∝t0.37 due to growth stabilization. Hence, the XRD and AFM data have revealed the existence of two growth regimes, and indicate that there is a strong link between the film structure and crystallinity and the film growth mode.