Carbon nitride thin films deposited by reactive plasma beam sputtering

Carbon nitride thin films have been deposited on silicon substrates by reac tive sputtering of a pure graphite target. In this process, argon plasma, g enerated by a hot cathode discharge, diffuses through a diaphragm into a de position 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 characteriz ed by X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red s pectroscopy (FTIR) and Raman spectroscopy. The atomic ratios of N and C in films are evaluated by XPS. At high N, partial pressure, the atomic fractio n saturates at a value of 38 at.%. The curve fitting of the C Is and N Is X PS 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 t wo amorphous carbon nitride phases in films, one with a stoichiometry simil ar to C3N4 and the other with an increasing fraction of nitrogen as the tot al N content in the films increases. These two carbon nitride phases seem t o be present as soon as nitrogen is incorporated in films, even at low atom ic concentration of nitrogen. (C) 2000 Elsevier Science S.A. All rights res erved.