Ž . Surface and Coatings Technology 142144 2001 874880 Synthesis of carbon nitride films by high-density helicon wave-excited plasma sputtering Y. Setsuhara a,  , Y. Sakawa b , T. Shoji b , M. Kumagai c , S. Mikaye a a Joining and Welding Research Institute, Osaka Uni  ersity, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan b Department of Energy Engineering and Science, Nagoya Uni  ersity, Furo-cho, Chikusa-ku, Nogoya 464-8603, Japan c Kanagawa Industrial Technology Research Institute, 705-1 Shimo-Imaizumi, Ebina, Kanagawa 243-0435, Japan Abstract Properties of high-density nitrogen plasmas with excitation of the m 0 mode helicon wave has been studied for reactive plasma sputter synthesis of carbon nitride films. High-density nitrogen plasmas with densities of 4 10 12 cm 3 were obtained in Ž . nitrogen at 0.1 Pa. Optical emission spectroscopy showed that the line emissions of atomic nitrogen NI and atomic-nitrogen Ž . ions NII were considerably enhanced in the helicon wave-excited high-density plasma, whereas, the spectra measured from the Ž . induction-mode non-wave excitation low-density plasma were dominated by those of the molecular band emission associated Ž . with the first positive system of N . Carbon nitride films have been deposited on Si 100 substrates by reactive sputtering of 2 carbon target with the helicon wave-excited high-density nitrogen plasmas at 0.1 Pa. Compositional characterizations of the Ž . CN films were performed using Rutherford backscattering spectrometry RBS . The RBS analysis showed that the NC ratio of 1.3 was achieved by depositing the CN films at plasma densities as high as 1 10 12 cm 3 , where the line emissions of atomic nitrogen were significantly higher than the molecular band emissions. Increase in the plasma density andor the emission-inten- Ž . sity ratio of the atomic nitrogen NI to the molecular band in the vicinity of the substrate was found to directly contribute to the Ž . NC composition ratio in the CN films. Structural analysis by Fourier transform infrared spectroscopy FTIR showed that the bonds associated with hydrogen impurity could be effectively eliminated by increasing the substrate temperature during film depositions.  2001 Elsevier Science B.V. All rights reserved. Keywords: Helicon plasma; Carbon nitride film; High-density nitrogen plasma; Plasma sputtering; Optical emission spectra 1. Introduction Studies on the synthesis of superhard nitride films in Ž . B C N atomic system c-BN, CN and BCN have attracted great interests due to their potentially- andor theoretically-expected extreme properties similar or   even superior to those of diamond 1,2 . Motivated by the desire to establish a nitridation environment with  Corresponding author. Tel.: 81-6-6879-8661; fax: 81-6-6879- 8689. Ž . E-mail address: setuhara@jwri.osaka-u.ac.jp Y. Setsuhara . extremely high reactivity for the synthesis of these metastable covalent materials, we have developed a high-density helicon wave-excited plasma source de- signed for sputter deposition to supply high concentra-   tion of atomic nitrogen 3,4 . The significance of the atomic nitrogen for the formation of the metastable superhard nitrides is expected from the fact that the radiative de-excitation lifetime of the higher vibrational mode of the excited nitrogen molecule is considerably shorter than the characteristic diffusion time of the gas species from the plasma source region to the substrate  4. Helicon wave-excited plasma generation has at- 0257-897201$ - see front matter  2001 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 2 5 7 - 8 9 7 2 01 01119-7