Amorphous hydrogenated carbon nitride films deposited via an expanding thermal plasma at high growth rates

An expanding thermal plasma of argon and nitrogen into which acetylene is i njected, was used to deposit amorphous hydrogenated carbon nitride (a-C:N:H ) films. In the absence of an external bias high growth rates (up to 37 nm/ s) were achieved. The growth rate and refractive index of the films were st udied in situ with HeNe-ellipsometry. Fourier transform infrared (FTIR) abs orption spectroscopy was used to investigate the different bondings. The ch anges observed in the infrared absorption spectrum with increasing N-2/C2H2 ratio in the plasma indicate an increase in dehydrogenation of the films l eading to polymerization, and possibly also to graphitization. The microhar dness and Young's modulus, as determined by nano-indentation measurements, show a strong respectively overall increase with increasing acetylene flow, and appear to decrease on addition of N-2. This is attributed to the incre ase in the polymerization of the films on incorporation of nitrogen. Evalua tion of the chemical composition by Rutherford back scattering (RBS) and el astic recoil detection analysis (ERDA) reveals that a deposition mechanism should be considered in which N and H are in competition with each other du ring growth. (C) 1998 Elsevier Science S.A. All rights reserved.