Internal stress reduction by nitrogen incorporation in hard amorphous carbon thin films

Results of a study on internal stress, hardness, and structure of nitrogen-doped amorphous hydrogenated hard carbon films deposited by rf glow discharge from methane-nitrogen mixtures onto silicon substrate are presented. Films obtained for different N2 partial pressures (bias voltage Vb=−370 V and total pressure P=8 Pa) were characterized by infrared spectroscopy, Raman scattering, and nuclear techniques. The elemental composition, density, and structure are correlated with Vickers hardness and internal stress values, obtained from the substrate bending method. It has been observed that internal stress considerably decreases with increasing nitrogen content, in contrast to hardness, structure, and hydrogen concentration, which remain unchanged.