Reactively sputter-deposited Mo–Ox–Ny thin films

Thin films of Mo–Ox–Ny were produced by reactive direct current (dc) magnetron sputtering of molybdenum in an Ar–N2–O2 gas mixture. The effects of oxygen incorporation on the residual stress and structural properties of these films as well as the influence of post-deposition annealing have been studied. These films were characterized ex situ in terms of their core electron bonding configuration and atomic concentrations by X-ray photoelectron spectroscopy (XPS), their microstructure by X-ray diffraction (XRD), transmission electron microscopy (TEM), transmission electron diffraction (TED), and their stress in situ by a wafer curvature-based technique. It was found that the stoichiometric face-centered cubic (fcc) Mo2N films deposited under oxygen-free conditions had a high compressive stress of 1.38 GPa. The compressive stress in Mo–Ox–Ny films decreased significantly with an increase in the oxygen concentration and became slightly tensile for films reaching ∼10 at.% oxygen. The films had almost zero stress at 16–20 at.% oxygen. These results can be ascribed to the decrease in the lattice parameter caused by incorporating small oxygen atoms in the lattice sites and the development of an amorphous network in the Mo–Ox–Ny films as the incorporation of oxygen was increased. It was also found that the oxygen-contained Mo–Ox–Ny films were thermodynamically more stable than the oxygen-free films. The effect of oxygen in stabilizing the Mo2N structure was also elucidated and explained on the basis of structural and thermodynamic stability.