DLC Coatings by PI3D: Low-Voltage versus High-Voltage Biasing

Diamond-like carbon (DLC), in particular hydrogenated amorphous carbon (a-C:H) films have been formed on various conductive and dielectric materials by plasma immersion ion implantation and deposition ((PID)-D-3) processing. Effect of pulse voltage and other process parameters on the film properties was investigated. It was found that for conductive substrates, a low-voltage (approximate to 1 kV), high repetition rate pulsing provides better overall film performance comparing to that obtained by applying higher voltages, which is also favourable for conformal treatment of 3D workpieces. However, short 1-2 mu s, high-voltage 5-20 kV pulses are required for dielectric workpieces several millimeter thick. Good film adhesion was achieved by forming a Si-containing buffer layer using hexamethyldisiloxane (HMDSO) as a precursor and a low-voltage pulsing. Roughness and wettability of DLC coatings was found to be controlled by varying the bias specs and sample temperature. Very smooth films with average roughness less than 1 A were prepared at optimised process parameters.