Yun-Sik JIN*, Yoshinobu MATSUDA and Hiroshi FUJIYAMA

Department of Electrical Engineering and Computer Science, Nagasaki University
1-14 Bunkyo, Nagasaki 852-8521, JAPAN
ysjin@ec.nagasaki-u.ac.jp

The current interest in carbon nitride (CNx) films has been started from the theoretical work by Liu and Cohen [1] predicting extreme hardness of this material. Most of the studies that have been used to synthesize carbon nitride films are based on vapor phase methods. Carbon nitride films deposited by magnetron sputtering of carbon target in a nitrogen atmosphere are hard, wear resistant and have a low friction coefficient [2].

In this study, we report on the effect of process parameters on the properties of carbon nitride films. Carbon nitride films have been deposited on a Si (100) wafer by reactive sputtering of a graphite target with nitrogen and/or argon gases. Modified cylindrical type DC magnetron was used as sputter deposition source. The deposition rate changed by a gas-mixing ratio of nitrogen to argon and by a substrate bias voltage (DC and RF). The nitrogen to carbon ratio (N/C ratio) in the film evaluated by x-ray photoelectron spectroscopy (XPS) ranged from 0 to 0.5. The analysis of chemical bonding state, which was performed by XPS, Fourier transform infrared (FT-IR) spectroscopy, revealed that carbon and nitrogen formed a strong bonding in our film. Raman spectra obtained from deposited films showed two peaks corresponding to G band and D band at around 1585 cm-1 and 1380 cm-1 respectively. The relative Raman intensity of D and G band (ID/IG) increased with RF substrate bias voltage, which indicates the ion bombardment effect on growing film.

[1] A. Y. Liu and M. L. Cohen, Science, 245 (1989) 841
[2] D. Li, E. Cutiongco, Y. W. Chung, M. S. Wong and W. D. Sproul, Surf. Coat. Technol., 68/69 (1994) 611