Preparation and characterization of thin cubic boron nitride films

The goal of our work was to develop d.c. magneton sputter process for the c-BN deposition. For the experiments especially boron carbide (B4C) were used. The process development was subdivided in different phases. As first a r.f. diode sputtering process was optimized for a h-BN target and transferred to a B4C target, followed by d.c. magnetron sputtering experiments with the B4C target. Essential process parameters for the c-BN deposition are the relative reactive gas flow, the ion energy and the ion current density at the substrate. The adhesion of c-BN is stongly limited by compressive stress. One way to reduce the stress might be that after the nucleation of the cubic phase the process parameters will be changed to more 'softer' conditions. We observed the nucleation of the cubic phase in situ by measuring the substrate currents. Several film properties like hardness, electrical conductivity or electron emission behaviour were investigated.