Deposition of B-C-N ternary films by means of sputtering-PBII hybrid system

In this experiment, the authors aimed at forming ternary system B (Boron) -C (Carbon) -N (Nitrogen) films on an Si (100) substrate using the sputtering-PBII hybrid system with boron target and Ar+N₂+CH₄ mixed gas as raw material. We formed different B-C-N films with various compositions by the carbon concentration control, with the target applying RF power at the time of film production as 300w and substrate DC pulse bias and RF electric power to be applied to the substrate as -5 kV and 300 W, by changing CH₄ gas flow ratio in the range between 0-13 %. For this B-C-N film, the relationship between B-C-N compositions and structure in the film and mechanical characteristics was discussed based on bonding state evaluation by FT-IR, nano-indentation hardness test, internal stress measurement and frictional wear test. Composition ratios of the formed B-C-N film were BC_1.2N, BC_1.9N_1.1, BC_2.4N_1.3, BC_2.8N_1.4 and BC_3.6N_1.7. The carbon concentration was controlled in the range between 35-70 at%, and the B/N ratio was 0.6-1.0 here, indicating that it was comprised of a ternary system of B-C-N. Two absorption peaks of h-BN frequent seen in a B-C-N film were observed in IR spectra. Shift and broadening of the peak position accompanied with an increase in the carbon concentration were also seen and the above-mentioned peaks suggest change in bonding states in the films. For internal stress of the B-C-N films, it has been clarified that the BC_1.9N_1.1 films with the carbon concentration of 48 at% showed the maximum value (1.1 GPa) and the compositions with carbon concentrations above or below 48 at% tended to decrease. For such change in this internal stress, nano-hardness of the B-C-N films slightly rose compared with BN while it was only around 15 GPa, with no clear differences shown. The friction coefficient fell from 0.25 to around 0.15 with an increase in carbon concentrations for the B-C-N films with carbon concentrations of over about 50at%. Here, the specific wear rate was approximately 10⁻⁷ mm³/Nm, indicating superior wear resistance.