FORMATION OF BORON-NITRIDE FILMS WITH VARIOUS AMOUNTS OF THE CUBIC PHASE

Boron nitride films with various structures have been prepared by low( 500-700 eV) and medium energy (5000 eV) ion assisted evaporation on he ated silicon substrates. Besides pure nitrogen gas, a mixture of argon /nitrogen was used. By changing the ion current density profile over t he substrate area different film types can be grown in one vacuum run. Fourier Transformed Infrared Spectroscopy was carried out to collect information about the B-N bond-structure. For the control of the film stoichiometry and impurity contents Auger Electron Spectroscopy depth profiling analyses were conducted. X-ray Diffraction (XRD) data indica ted the effect of different growth conditions (ion current density, io n energy, substrate temperature, gas mixture) on the orientation of th e initial h-BN layer. As BN is a potential candidate for tribological applications, the surface topography of films is of major interest. Fr om high resolution Scanning Electron Microscopy (up to 80 000-fold mag nification) experiments, information about the effect of the growth co nditions on the surface topography was obtained. Profilometer scans in connection with the other characterisation techniques let us get insi ght into different failures of the film adhesion. At 700 eV ion energy , Ar/N-2 gas mixtures of 40:60 vol.% and substrate temperatures of 450 degrees C, boron nitride films with more than 80% cubic phase content could be grown. At drastically reduced substrate temperatures of 250 degrees C; the c-BN growth was also successful. The results are discus sed in the light of the effect of the ion assisted processes not only on the cubic phase evolution, but also on the degree of formation of a n oriented initial h-BN layer, as monitored by XRD. (C) 1997 Elsevier Science S.A.