INFRARED ELLIPSOMETRIC CHARACTERIZATION OF MIXED-PHASE BN LAYERS DEPOSITED BY PLASMA-ENHANCED PHYSICAL VAPOR-DEPOSITION

The hollow cathode are (HCA) is characterized by a high electron density and the existence of beam electrons, properties useful for plasma activated deposition processes. Calculations of the power transferred to boron show that solid boron can be heated up by the HCA plasma beam in a few minutes to a temperature where the electrical resistance becomes very small. A HCA evaporation device is applied to form boron nitride layers on different substrate materials. The films were characterized by Fourier transform infrared spectroscopy as well as electron and X-ray diffraction. The boron evaporation rate was kept nearly constant while the nitrogen pressure varied between 0.013 Pa and 0.27 Pa. At nitrogen pressures of p(N2)=0.08 Pa and p(N2)=0.13 Pa the layers were found to consist in part of the cubic phase. An infrared ellipsometer with a spectral range from 400 cm(-1) to 3500 cm(-1) was set up as an additional layer characterization method. As an example for nontransparent samples the infrared reflectance spectrum of a BN coated steel plate is shown.