Highly conductive carbon film deposition by DC and microwave power superposition

 Highly conductive carbon film, a carbon film including high ratio of graphite-like structure (sp² bond), is attractive material because of its superior properties such as its high electrical conductivity, anti-corrosion, low friction and so on. For the enhancement of the electrical conductivity of the film, higher ion flux as well as higher ion energy is required. In this study, high-density microwave plasma with high negative bias voltage source (<2 kV) was applied to deposit conductive carbon films.  A vacuum vessel of 50 cm in length was equipped with a quartz plate (50×17 cm²) and was evacuated by a dry pump. Argon gas was introduced into the vessel through a mass flow controller and vaporized benzene (C₆H₆) was fed through another gas manifold at 3 cm away from the quartz plate toward a water-cooled substrate stage. In this study, the stage is negatively biased by a high impulse voltage generator (-2 kV, pulse frequency: 500 Hz, duty 10%). Film conductivity showed film sheet resistance drastically decreased at the bias voltage of ~ 1 kV, and was as low as 10²W/sq. at 2 kV. Film conductivity was almost uniform at a length of ~20 cm along the waveguide direction.