NITROGEN INCORPORATION INTO HARD AMORPHOUS-CARBON FILMS OBTAINED BY RF PLASMA DECOMPOSITION OF CH4-N-2 GAS-MIXTURES

Recent results on the incorporation of nitrogen into amorphous hydroge nated carbon films (a-CNx:H) are reviewed. The films are deposited ont o silicon substrates by rf plasma decomposition of methane-nitrogen mi xtures. The samples are characterized by a combination of analytical t echniques: nuclear techniques (RES, NRA, and ERDA), SIMS, infrared abs orption, Raman scattering, and positron annihilation spectroscopy (Dop pler broadening method). The Vickers hardness and the internal stress of the films are also determined. The results indicate that the incorp oration of nitrogen increases the density of voids and induces a progr essive graphitization of the films. The incorporation of nitrogen up t o 11 at% reduces the internal stress of the films without significant modification of the film hardness. Results on the thermal stability of a-CNx:H films are also presented: for annealing temperatures higher t han 300 degrees C, hydrogen and nitrogen losses occur as well as the g raphitization of the films.