Reactive magnetron sputter deposited CNx: Effects of N-2 pressure and growth temperature on film composition, bonding, and microstructure

The effects of growth processes on the chemical bond structure, microstructure, and mechanical properties of carbon-nitride (CN,) thin films, deposited by reactive magnetron sputtering in a pure N-2 discharge, are reported. The film deposition rate R(D) increases with increasing N-2 pressure P-N2 while N/C ratios remain constant. The maximum N concentration was similar to 35 at.%. R(D) was found to be dependent upon the film growth temperature T-S. For a given P-N2, R(D) decreased slightly as T-S was increased from 100 to 600 degrees C. The variations in R(D) with both PN2 and T-S can be explained by ion-induced desorption of cyano radicals CN, from both the target and growth surfaces during deposition. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy (FTIR) analyses showed that N atoms in films grown at T-S>350 degrees C with low nitrogen partial pressures P-N2, similar to 2.5 mTorr, were bound to C atoms through hybridized sp(2) and sp(3) configurations. For low T-S=100 degrees C and higher P-N2 10 mTorr, triple-bonded C=N was detected by FTLR. Two types of microstructures were observed by high-resolution transmission electron microscopy, depending on T-s: an amorphous phase, containing crystalline clusters for films deposited at T-S=100 degrees C, while a turbostraticlike or fullerenelike phase was observed for films deposited at T-S > 200 degrees C CNx films deposited a higher T-S and lower P-N2 were found to have higher hardness and elastic modulus. (C) 1996 American Vacuum Society.