Phase formation and structure of magnetron sputtered chromium nitride films: in-situ and ex-situ studies

The effects of deposition conditions on phase formation, crystallographic characteristics, residual stress, and morphology of chromium nitride films have been studied. The films were prepared via reactive magnetron sputtering with a confocal deposition geometry. The geometry is compatible with an X-ray diffraction system, which allows the growing films to be studied in-situ and in a quasi-real time fashion. The use of the unique film growth/characterization system indicates that in-situ X-ray diffraction can be a useful tool for in-situ monitoring film depositions at various growth stages. In addition to in-situ diffraction studies, the grazing incidence X-ray scattering (GIXS) with synchrotron radiation, pole figures, double crystal diffraction topography (DCDT) and scanning electron microscope were also used to characterize the post-deposited films. The effect of nitrogen flow on phase formation can be described based on three ranges of nitrogen flows. With low nitrogen flows, the films consist of primarily BCC Cr phase or hexagonal β-Cr2N. Growth at moderate nitrogen flows leads to the films of N-deficient cubic CrN1−x. With high nitrogen flow, the deposition results in films of nearly stoichiometric CrN with the (111) type texture. In particular, the processing window for Cr2N appears to be very small, in comparison with CrN, which can be readily obtained at high nitrogen flows. Thus the films of single Cr2N phase with well-defined β structure can only be obtained under strictly controlled conditions.