GROWTH AND CHARACTERIZATION OF BORON-NITRIDE THIN-FILMS

Boron nitride layers were deposited using ion beam assisted deposition with different ion energies (0.5 or 1.5 keV) and normal angle of inci dence on silicon wafers heated to 400 degrees C. By mounting the elect ron beam evaporator at an angle of 56 degrees to the normal of the sub strate, it was possible to investigate the influence of the continuous ly changing ion-to-atom ratio on the grown modification and, subsequen tly, to determine the properties of the BN films. The coatings were ch aracterised using polarised IR reflection spectroscopy, heavy ion elas tic recoil detection and microhardness measurement (Vickers indenter). The dynamic hardness of the Si substrate could be almost doubled with an approximately 1000-Angstrom thick c-BN coating. The transition det ermined by IR spectroscopy from non-cubic to cubic growth could be cle arly resolved across the 3-inch silicon substrate. As soon as the spec tra recorded with p-polarised light exhibited the reflection band of t he cubic phase at 1100 cm(-1), an additional feature appeared in the i n-plane stretching h-BN mode near 1580 cm(-1). The two features of the h-BN LO band might be due to the layered growth of the BN system corr esponding to two different dielectric constants of the h-BN layer near the interface and at the sp(2)-bonded grain boundaries of the c-BN-co ntaining overlayer. Furthermore, coatings with a high cubic fraction e xhibited a stoichiometric boron-to-nitrogen ratio with small oxygen an d hydrogen contaminations.