Morphological features of diamond-like carbon films deposited by plasma-enhanced CVD

Diamond-like carbon (DLC) films have been deposited by asymmetric capacitively coupled radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) system. The morphological features of DLC films depending on the methane pressure and substrate bias voltage have been studied systematically by atomic force microscopy (AFM). In low pressure and low bias voltage range, the DLC film is rough, due to some micro-particles formation in the film. With increasing pressure and bias voltage, the films become smooth and particle free. With increasing self-bias voltage, first the hardness of the films increases, reaches a maximum around 250 V, then decreases; the roughness of the films decreases greatly (below 250 V), then decreases slightly (above 250 V). With increasing gas pressure, the hardness of the films increases first, reaches a maximum in the range of 10-100 mTorr, then decreases; the roughness of the films decreases greatly, reaches a minimum (10-100 mTorr), then increases. The mechanism of formation of the morphological features in the DLC films made under different deposition conditions is discussed.