Growth, microstructure and electronic properties of amorphous carbon nitride films investigated by plasma diagnostics

Abstract

Amorphous nitrogenated carbon films are prepared in a dual electron cyclotron resonance-radio frequency plasma from a mixture of methane and nitrogen gas. A marked variation of electronic properties and microstructure of the films as a function of nitrogen concentration is observed from Fourier transform infrared (FTIR) spectra, electron energy loss spectra, optical absorption spectra, x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and electrical conductivity. From the variation of intensity of different positive ions and neutral radicals, using quadrupole mass spectroscopy and optical emission spectroscopy, the growth rate, structure and properties of the films are investigated. The density of methyl (CH3) radicals and the film growth rate are found to decrease with the increase of nitrogen concentration. A correlation between the C/N atomic ratio in the films and CH/CN and also CH/N ratio in the plasma is noticed. Also, the CH radical intensity in the plasma and the amount of CH bonds in the films, observed from FTIR spectra, vary in a similar fashion as a function of nitrogen concentration. A model describing film growth and nitrogen incorporation in the films is proposed.