A concept for the deposition of adherent cubic boron nitride films

Measures to reduce the high compressive stress of c-BN films and to improve their adhesion are discussed. A simple model of stress formation in c-BN films reveals that high ion energies and low Ar/N 2 ratios should be used for stress reduction. These predictions are experimentally confirmed by means of depth resolved stress measurements using back-etching techniques with films deposited on cantilever substrates for accurate stress measurements. By suitable choice of ion energy and Ar/N 2 ratio, the stress can be reduced by a factor of four to values below 5 GPa. The adhesion of c-BN films, on the other hand, can be improved by engineering the interface; controlled surface roughening and the deposition of gradient interlayer B→BN both lead to better adhesion. Based on these results, a multi-step process is proposed for the deposition of thick, well-adherent c-BN films.