CHARACTERIZATION OF CARBON NITRIDE THIN-FILMS DEPOSITED BY A COMBINEDRF AND DC PLASMA BEAM

Thin carbon nitride films have been deposited on silicon(100) substrat es downstream of a nitrogen plasma beam generated in a combined RF (13 .56 MHz, 40-50 W) and DC (voltage +/-200 V, power 1-10 W) discharge be tween a graphite electrode and a graphite nozzle. By combining the RF and DC sources the capability of rf field to create extended plasmas i s used together with the enhanced sputtering and biasing effect of the DC source. The plasma characteristics (electron temperature, presence of molecular species) have been studied by optical emission spectrosc opy. Deposition rates of 2.5-3 nm/s are obtained at the centre of the plasma beam and at a few centimetres distance from the nozzle. The fil ms have been investigated by X-ray photoelectron spectroscopy, spectro scopic ellipsometry, scanning and transmission electron microscopy, an d microhardness measurements. The films have an overall N:C ratio of 0 .28 but the distribution of different nitrogen bonds depends upon the DC bias conditions. In the spectral range 0.3-0.7 mu m the refractive index increases slightly from 1.5 to 2.2. The films are amorphous, wit h morphology consisting of a columnar structure. The columns have a di ameter of about 20 nm. A hardness of 24 GPa has been measured. (C) 199 8 Elsevier Science S.A. All rights reserved.