Internal stress of a-C:H(N) films deposited by radio frequency plasma enhanced chemical vapor deposition

Amorphous hydrogenated carbon nitride [a-C:H(N)] films were deposited from the mixture of C2H2 and N-2 using the radio frequency plasma enhanced chemical vapor deposition technique. The films were characterized by X-ray photon spectroscopy, infrared, and positron annihilation spectroscopy. The internal stress was measured by substrate bending method. Up to 9.09 at% N was incorporated, in the films as the N,content in the feed gas was increased from 0 to 75%. N atoms are chemically bonded to C as C-N, C=N and C=N bond. Positron annihilation spectra shows that density of voids increases with the incorporation of nitrogen in the films. With rising nitrogen content the internal stress in the a-C:H(N) films decrease monotonically, and the rate of decrease in internal stress increase rapidly. The reduction of the: average coordination number and the relax of films structure due to the decrease of H content and sp(3)/sp(2) ratio in the films, the incorporation of nitrogen atoms, and the increases of void density in a-C:H(N) films are the main factors that induce the reduction of internal stress. (C) 1999 Elsevier Science S.A. All rights reserved.