Abstract :
CrNx thin films have attracted much attention for semiconductor IC packaging molding dies and forming tools due to their excellent hardness,
thermal stability and non-sticking properties (low surface free energy). However, few data has been published on the surface free energy (SFE) of
CrNx films at temperatures in the range 20–170 8C. In this study CrNx thin films with CrN, Cr(N), Cr2N (and mixture of these phases) were prepared
using closed field unbalanced magnetron sputtering at a wide range of Cr+2 emission intensity. The contact angles of water, di-iodomethane and
ethylene glycol on the coated surfaces were measured at temperatures in the range 20–170 8C using a Dataphysics OCA-20 contact angle analyzer.
The surface free energy of the CrNx films and their components (e.g., dispersion, polar) were calculated using the Owens–Wendt geometric mean
approach. The influences of CrNx film surface roughness and microstructure on the surface free energy were investigated by atomic force
microscopy (AFM) and X-ray diffraction (XRD), respectively. The experimental results showed that the lowest total SFE was obtained
corresponding to CrN at temperature in 20 8C. This is lower than that of Cr(N), Cr2N (and mixture of these phases). The total SFE, dispersive SFE
and polar SFE of CrNx films decreased with increasing surface temperature. The film roughness has an obvious effect on the SFE and there is
tendency for the SFE to increase with increasing film surface roughness.
