Surface roughness, mechanical properties and bonding structure of silicon carbon nitride films grown by dual ion beam sputtering

Silicon carbon nitride (SiCN) films were deposited by dual ion beam sputtering (DIBS) of SiC target in mixed Ar/N2 atmosphere at 100 °C. The surface roughness and the mechanical properties of the SiCN films were measured by using non-contact surface profilometer and nano-indenter. The bonding structure for the SiCN films was analyzed using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. The influences of assisting ion beam energy and concentration on surface roughness, mechanical properties and bonding structure of the SiCN films were discussed systematically. The results showed that the variations of surface roughness and hardness for the SiCN films with the assisting ion beam energy were in the range of 7–27 nm and 23–29 GPa, respectively. With an increase in the nitrogen ion beam concentration, the film surface roughness first decreased to a minimum value, and then increased, while the hardness first increased to a peak value, and then decreased. When the assisting ion beam energy and concentration were 300 eV and 0.5, the SiCN film possessed the low surface roughness of 11 nm and the highest hardness of 29 GPa, its atoms ratio, C:Si:N:O was about 1:0.42:0.18:0.32. The bonding structure of the SiCN films mainly consisted of Si–C, Si–N, C–N, CN and CC bonds and corresponded to a network of the mixed sp2/sp3 hybridized bonds with the units of Si(C4), Si(N4) and Si(C4−nNn). The film mechanical properties were correlated to the proportion of Si–C, Si–N, CN and C–N bonds in the SiCN films.