Influence of substrate dc bias on chemical bonding, adhesion and roughness of carbon nitride films

Carbon nitride (CNx) films had been grown on Si (0 0 1) substrates using rf magnetron sputtering method in pure N2 as substrate bias (Vb) was varied from 0 V to −150 V and substrate temperature (Ts) kept at a constant of 350 °C. The chemical bonding states of CNx films were characterized using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). It was observed that a predominant formation of sp3 CN bonds occurred in carbon nitride films grown at bias of −50 V. The scratch test was utilized for measurement of CNx coating adhesion on Si (0 0 1), and then the morphology of the films was analyzed using atomic force microscopy (AFM) experiments. The results revealed that CNx films grown at Vb=−100 V, having the smoothest surface with the lowest rms roughness of 0.75 nm, adhered much more strongly to the Si (0 0 1) substrate than at other substrate bias values. Furthermore, the effect of ion bombarding on the adhesion and roughness of CNx films on Si (0 0 1) was discussed.