Si-containing crystalline carbon nitride derived from microwave plasma-enhanced chemical vapor deposition

Carbon nitride thin films have been grown by the microwave plasma-enhanced chemical vapor deposition (MW-PECVD) technique.
Gas mixtures containing CH4, H 2 and NH 3 at various ratios were tested as precursors, and Si (t00) wafers were used as substrates. X-ray
photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), electron microscopy (both SEM and TEM), and Raman
spectroscopy have been employed to characterize the resultant films. The phase contents in the films were found to be strongly dependent
on the substrate temperature. The incorporation of significant amounts of Si into the film was observed when the substrate temperature
exceeded 1000 °C. However, the presence of Si along with a high substrate temperature also promotes the formation of large crystallites.
XPS analyses of C(ls) and N(ls) core levels suggest a multiple bonding structure between carbon and nitrogen atoms. Microscopic
investigations of the films reveal the coexistence of large grain (> 10 ~zm) and fine grain (< 1 ~m) crystals. Preliminary structural
studies suggest the presence of a crystalline carbon nitride compound corresponding to a hypothetical e~-C3N 4 phase (isomorphic to
et-Si3N4), which may also be a stable hard material. Furthermore, we propose that some of the Si has been incorporated as a
substitutional element for the C site in the new phase. The Raman spectra exhibit many sharp lines, of which the most distinct ones mimic
those of the (x-Si3N 4 structure. © 1997 Elsevier Science S.A.