Carbon nitride thin films deposited by reactive plasma beam sputtering

Carbon nitride thin films have been deposited on silicon substrates by reactive sputtering of a pure graphite target. In this process, argon plasma, generated by a hot cathode discharge, diffuses through a diaphragm into a deposition chamber towards the target which is biased at - 300 V. The current density on the target is about 30 mA cm(-2). Nitrogen gas is injected into the deposition chamber during the sputtering. Evolution of the deposition rate is measured versus the partial N(2) pressure. The films are characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red spectroscopy (FTIR) and Raman spectroscopy. The atomic ratios of N and C in films are evaluated by XPS. At high N, partial pressure, the atomic fraction saturates at a value of 38 at.%. The curve fitting of the C Is and N Is XPS peak spectra indicates that C and N atoms in films exhibit two different chemical states, representative of different C-N chemical bonds. These XPS results, combined with FTIR and Raman analysis, suggest the existence of two amorphous carbon nitride phases in films, one with a stoichiometry similar to C(3)N(4) and the other with an increasing fraction of nitrogen as the total N content in the films increases. These two carbon nitride phases seem to be present as soon as nitrogen is incorporated in films, even at low atomic concentration of nitrogen. (C) 2000 Elsevier Science S.A. All rights reserved.