Ultrathin CN_x Overcoats for 1 Tb/in² 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 rotating holder that allowed 45° tilt angle and substrate rotation about the surface normal up to 20 rpm. AFM scans over 10×10 μm² showed that 50 nm thick CN_x films prepared under optimum substrate bias conditions have r.m.s. surface roughness almost four times lower than those prepared without substrate tilt and rotation. We observed a two-fold reduction in corrosion damage for hard disk substrates with 1 nm 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.