CHEMICAL AND COMPOSITIONAL CHANGES INDUCED BY N+ IMPLANTATION IN AMORPHOUS SIC FILMS

The effects of 30 keV N+ implantation in amorphous silicon carbide fil ms deposited on silicon substrates by rf sputtering over a fluence ran ge of 1 x 10(16)-2 x 10(17) ions cm-2, are studied by means of x-ray p hotoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), an d infrared (IR) absorption techniques. The ion-induced modifications o f these films have been investigated on the basis of the chemical stat e evolution of Si, C, and N (using XPS and AES) and on the basis of th e vibrational features of the films components (using IR absorption). The results show that implanted N bonds Si selectively, substituting t he C atoms in the silicon carbide, and the C substitution by N results in a composite layer of carbonitrides and free C. An ion-induced C tr ansport has also been observed and correlations are established betwee n the formation of silicon carbonitrides and the dynamical behavior of the C in the implanted layer. the latter appears as a superposition o f (a) a chemically induced atomic redistribution, required by local st oichiometry and space-filling possibilities in an amorphous network, a nd (b) a radiation-induced redistribution, a mechanism that is prevail ing at low-fluence implantation.