Deposition of nanocomposite CNx/SiO2 films in inductively coupled r.f. discharge

Hard films were deposited in an inductively coupled r.f. discharge at a frequency of 3.5 MHz by the chemical transport of carbon from a graphite target in a nitrogen atmosphere combined with evaporation from a quartz tube. The nitrogen flow was varied from 1.0 to 4.0 seem. The r.f. power supplied was in the range 2.5-3.5 kW. Silicon substrates were placed on the graphite holder whose temperature was 700-800 degrees C. In the emission spectra the CN, N-2 and C-2 molecular bands and the silicon, carbon, oxygen and nitrogen atomic lines were observed. The ratio of nitrogen to carbon in the films ranged from 0.1 to 0.55 while the ratio of oxygen to silicon was about 2 for all the films studied. The films had a maximum hardness of 35 GPa and they showed a high elasticity up to 88%, good fracture toughness and adhesion to the substrate. Unlike carbon nitride films the CNx/SiO2 films were almost non-absorbing in the visible range. (C) 2000 Elsevier Science S.A. All rights reserved.