Columnar growth of ALN by r.f. magnetron sputtering: Role of the {1 0 1¯ 3} planes

Aluminum nitride films prepared by radio frequency magnetron reactive sputtering are usually columnar films with a {0 0 0 2} fiber texture. However, an original homogeneous nanostructural growth mode was observed in this study. The description of the shape of the grains in combination with crystallographic investigations reveals this growth mode is the result of an oblique growth perpendicular to the {1 0 1¯ 3} planes. Observations performed on feather-like grained films show that the {0 0 0 2} planes grow normally to the substrate and the {1 0 1¯ 3} planes grow at 32° away from the normal and perpendicularly to the axis of the branches of the feathers. The growth mode differs from the columnar one only by the shape of the formed grains. The width of the sub-grains ranges from 6 to 24 nm. The observation of this morphology allows us to propose a crystalline growth model of these films and more generally of the classical {0 0 0 2} textured columnar films. The morphologies and microstructures were investigated by scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The crystallographic texture was determined by X-ray diffraction pole figure measurement. Chemical study was performed by Auger electron spectroscopy and energy dispersive spectroscopy of X-rays.