ADHERENCE EXPERIMENTS ON CBN FILMS

Boron nitride thin films were deposited by tuned substrate rf magnetro n sputtering from an h-BN target. Pure Ar, 85% Ar+15% N-2 and Ar+10%<H -2<30% were used as processing gases. A threshold value of momentum pe r deposited atom was found, around 600 eV(1/2) amu(1/2), to obtain fil ms with a high content of the cubic phase (between 70 and 90%). By int roducing H-2 into the gas mixture, an attempt was made to improve stab ility of the films exposed to the air atmosphere, which was achieved a t 18% H-2 content. However, a decrease in cBN percentage, deduced from IR spectra, was observed. A 50% Ar+50% N-2 gas mixture was also used for ''in situ'' deposition of hBN coatings on cBN films. The resulting films exhibited longer lifetimes and different methods of delaminatio n, observed by SEM, than films without hBN coatings. Besides these att empts, different substrates were tested. B-doped (100)-Si showed great er stability than P-doped (100)-Si, and a buffer layer of 40 Angstrom Ni improved the adherence of 18% H-2 film. However, neither buffer lay ers consisting of diamond nor other Ni thickness, nor mechanical scrat ching of silicon with diamond and cBN powders, were successful. From X PS analysis, the B/N atomic ratio was estimated to be in the range of 1.05-1.10 for films obtained with 85% Ar+15% N-2 and 1.15-1.20 for fil ms deposited in pure Ar and in an Ar+H-2 atmosphere. (C) 1998 Elsevier Science S.A.