Ultrathin CN_x overcoats for 1Tb/in.² hard disk drive systems

Carbon nitride films were grown on silicon and hard disk substrates using pulsed dc magnetron sputtering in a single-cathode deposition system. Substrates were mounted on a specially designed holder that allowed 45° tilt angle and substrate rotation about the surface normal up to 20 rpm. The influence of substrate bias, substrate tilt, and rotation on film growth and properties was studied. Films with the lowest rms surface roughness and corrosion performance were obtained at -100V substrate bias with substrate tilt and rotation. Atomic force microscope scans over 10×10μm² sampling areas showed that 50 nm thick CN_x films prepared under these conditions have roughness almost four times lower than those prepared without substrate tilt and rotation. We observed a twofold reduction in corrosion damage for hard disk substrates with 1 nm thick CN_x overcoats deposited with substrate tilt and rotation. This improved performance is likely a result of more efficient and uniform momentum transfer parallel to the surface during deposition in this configuration.