Study of columnar growth, texture development and wettability of reactively sputter-deposited TiN, ZrN and HfN thin films at glancing angle incidence

Abstract

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 X-ray 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.