Characteristics of DLC films deposited by pseudo-spark discharge PE-CVD with different substrate bias voltages

Diamond-like carbon films were deposited on silicon wafers by a Pseudo-spark discharge (PSD) plasma-enhanced CVD method. Process gases were hydrogen and methane. For basic characteristics of the PSD, pressure range of the discharge was measured. As a result, it was confirmed that the discharge is formed on the left-hand side of the minimum point of the Paschen curve. The effect for the bias voltage of substrate on film structure, deposition rate and film hardness were also investigated by Raman spectroscopy, SEM and nano-indentation. In the Raman spectra, disorder (D) and graphite (G) are observed at around 1370 and 1580 cm^-1, respectively. The G-peak position and the area ratio of D-band to G-band (I(D)/I(G)) were decreased slightly as the bias voltage increased from -250 V to -325 V. The maximum deposition rate of 0.22 μm/h was obtained at the bias voltage of -300 V. Furthermore, Deposited film at -325 V exhibited the film hardness of 3.55 GPa. By increasing the substrate bias voltage, it was confirmed that the film characteristics was improved, too.