In this work, TiN, ZrN and HfN thin films fabricated using glancing angle deposition (GLAD) technique are studied both experimentally and by numerical simulations. The films (1 µm thickness) were deposited by reactive magnetron sputtering at 0.3 Pa and 300°C on Si substrates inclined at α=85° with respect to the target. The film morphology and crystal structure were characterized by scanning electron microscopy, atomic force microscopy and Xray diffraction (XRD), including pole figure measurements. The wettability of these coatings was investigated using the sessile drop method with three different liquids. It is shown that TiN, ZrN and HfN films have a cubic, NaCl-type crystal structure with a [111] out-of-plane orientation and exhibit a biaxial texture. XRD pole figures reveal that the crystal habit of the grains consists of {100} facets constituting triangular-base pyramids. The films develop columnar microstructures, with typical column widths of ~ 100 nm. The tilt angle β of the columns is found to increase from 24.5, 31.5 to 34° for TiN, ZrN and HfN films, respectively. Atomistic computations of the growth of these nitrides at glancing angle using a kinetic Monte Carlo model reveal that the growth morphology and variation in column tilt angle is well reproduced by considering the difference in the angular distribution of the sputtered particles.This study also shows that GLAD films are hydrophilic comparatively to the same films deposited at near-normal incidence, and among the three nitrides, TiN is the more wettable coating.
In this study, polycrystalline hafnium nitride (HfN) thin films were grown by oblique angle deposition (OAD) technique to investigate the relationship between column tilt angle, texture development and residual stress evolution with varying inclination angle α of the substrate. The films (~1 μm thickness) were grown at various angles (α = 5°, 25°, 35°, 65°, 75°, and 85°) with respect to the substrate normal by reactive magnetron sputtering at 0.3 Pa and 300 °C. The film morphology, crystal structure and residual stress state were characterized by scanning electron microscopy and X-ray diffraction (XRD), including pole figure and sin2ψ measurements. All HfN films had a cubic, NaCl-type crystal structure with an [111] out-of-plane orientation and exhibited a biaxial texture for α ≥ 35°. XRD pole figures reveal that the crystal habit of the grains consists of {100} facets constituting triangular-base pyramids, with a side and a corner facing the projection of the incoming particle flux (indicative of a double in-plane alignment). A columnar microstructure was formed for α ≥ 35°, with typical column widths of 100 nm. It is observed that the column tilt angle β increases monotonously for α ≥ 35°, reaching β = 34° at α = 85°. This variation at microscopic scale is correlated with the tilt angle of the (111) crystallographic planes, changing from −24.8 to 11.3° with respect to the substrate surface. The residual stress changes from strongly compressive (~−5 GPa at α = 5°) to negligible or slightly tensile for α ≥ 35°. The observed trends are compared to previous works of the literature and discussed based on existing crystal growth and stress models, as well as in light of energy and angular distribution of the incident particle flux calculated by Monte Carlo. Importantly, a decrease of the average kinetic energy of Hf particles from 22.4 to 17.7 eV is found with increasing α due to an increase number of collisions.
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