CHARACTERIZATION OF CARBON NITRIDE THIN-FILMS DEPOSITED BY REACTIVE DC MAGNETRON SPUTTERING ON VARIOUS SUBSTRATE MATERIALS

The effects of substrate material on structure, composition and mechan ical properties of carbon nitride thin films, deposited by reactive d. c. magnetron sputtering in N-2 discharge, have been studied. CNx films , with a nitrogen concentration between 15 and 30 at.%, were deposited at two different N-2 partial pressures (2.5 mTorr and 10 mTorr) on to a number of different substrate materials, SiO2, Si3N4, TiN, Ni and h igh-speed steel, kept at temperatures between ambient and 500 degrees C. The results show that the adhesion of CNx films to Ni and steel sub strates was very poor, especially at elevated temperatures, whereas in the case of SiO2, Si3N4, and TiN substrates, the adhesion was general ly good. The variation in growth rate was also found to be different d epending on which substrate was used. Atomic force microscopy (AFM) re vealed that the films grown at a lower pressure were very smooth with an rms roughness between 0.2 and 0.3 nm, whereas the roughness was mor e than one order of magnitude higher (2-10 nm) for films grown at 10 m Torr. Nanoindentation measurements showed that the films grown at the low pressure and above 200 degrees C were both hard and elastic as exp ected, based on previous results. The films grown at temperatures belo w 200 degrees C were much softer and less elastic. (C) 1998 Elsevier S cience S.A.