ROUGHNESS AND DEPOSITION MECHANISM OF DLC FILMS PREPARED BY RF PLASMAGLOW-DISCHARGE

Due to the attractive properties, diamond-like amorphous carbon (DLC) films have been developed as resist material for photo lithography and as hard coatings. For these applications flat surfaces are required. In this work, the surface morphology and the deposition mechanism of D LC films have been investigated. Using parallel plate r.f. plasma glow discharge, methane gas was decomposed for deposition of DLC films on the third electrode located perpendicularly to the two parallel plates . The DLC films were deposited on Si substrates at various distances f rom the plasma discharge and different bias voltages. IR spectra of th e DLC films were taken with an FTIR spectrometer. Determination of the roughness was performed by atomic force microscopy (AFM). An optical emission profile taken between plasma edge and substrate surface was e mployed to monitor the occurrence of neutral radicals. The roughness o f the DLC films strongly depends on the bias voltages, because the vol tage influences the acceleration energy of ionic species hitting the s ubstrate surface. Furthermore, the roughness of the samples depends on the distance between the substrate and the plasma discharge. Characte ristically, the roughness decreases with distance up to 20 mm after wh ich it increases again. From the result, the ratio of neutral and ioni c species was concluded to be very important for the flatness of the D LC films. In order to fabricate flat DLC films, it is very important t o control the energy of ionic species and the ratio between ionic spec ies and neutral radicals. (C) 1998 Elsevier Science Ltd. All rights re served.