FORMATION OF CBN FILMS BY ION-BEAM-ASSIST ED DEPOSITION

Cubic boron nitride (cBN) has many excellent properties, such as the h ighest hardness next to diamond, high electrical insulation and high t hermal conductivity. cBN films were deposited by IVD (Ion-beam-assiste d vapor deposition) method. Effects of the ion current density, the co mposition of the supplied gas into the ion source and pressure in the vacuum chamber on cBN formation were investigated. At a constant B dep osition rate, cBN was formed in a certain range of an ion current dens ity. XPS analyses showed that the cBN film has a stoichiometric compos ition of BN, and the diffraction patterns from cBN (111), (220) and (3 11) were observed by transmission electron diffraction. Under the cons tant ion acceleration voltage and the B deposition rate (0.5 kV, 0.13 nm s-1), cBN was formed when an Ar-based gas containing N2 of 20 to 80 % was supplied to the ion source. The deposition rate of cBN films was as high as about 5 x 10(-2) nms-1 and the range of the cBN formation conditions was wide when the Ar-based gas contained N2 of 36 to 50%. W ith increase of the pressure in the vacuum chamber, cBN formations wer e observed at lower ion current densities. We consider that this is du e to the charge exchange and not only ions but accelerated fast neutra ls also contribute to the cBN formation. Based on the above results, w e propose a map of the cBN formation conditions as functions of fast N 2 flux and fast Ar flux.