Amorphous hydrogenated carbon-nitride films prepared by RF-PECVD in methane-nitrogen atmospheres

In this work, films are deposited by PECVD-RF plasma using a gas mixture of CH4, N-2 and He or Ar. The Ar/CH4 and He/CH4 ratio is kept constant, while the nitrogen flow is allowed to vary. The samples were arranged in the anode plate as well as in the cathode plate. The effect of nitrogen addition on the films optical and structural properties of the films was analyzed by FTIR spectroscopy, UV-VIS-NIR spectroscopy, profilometry, ellipsometry and RBS. The intensities of the C=N (1600 cm(-1)), C=N (2300 cm(-1)) and NH (3250 cm(-1)) absorption bands, in the IR spectra, increase with the N-2/CH4 flow ratio. Samples deposited in the grounded electrode, show a decrease in the CH,, stretching band for increasing N-2/CH4 flow ratio, while the NH absorption bond increases, indicating that hydrogen is preferentially bonded to nitrogen. The C=N absorption increases for increasing N/C ratio; indicating that a nitrile phase is also formed. For the samples deposited in the powered electrode (Fig. 5), the CNH absorption band (1000-1700 cm(-1)) is much larger than the other bands (CHn and NH). The increasing signal in the 1000-1300 cm(-1) region suggests an increase in nitrogen bonding with sp(3) C. The C=N absorption is very small compared with the samples deposited in the grounded electrode. This behavior could be attributed to the increase in the methane and nitrogen radicals caused by stronger ion bombardment in the active electrode. (C) 2004 Elsevier B.V. All rights reserved.