Post-annealing effect in reactive r.f.-magnetron-sputtered carbon nitride thin films

Thin films of CN_x were deposited by reactive r.f.-magnetron sputtering on Si(100) substrates. The effect of annealing temperatures on the structural properties of the films has been studied by Fourier transform infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Both FTIR and XPS results show that the population of the carbon nitrogen phase decreases upon annealing in a vacuum. The XPS N 1s peaks indicate the component due to the carbon nitrogen bond to be significantly weaker than the others. An increase of the annealing temperature leads to a more prominent peak corresponding to the C-N phase in the FTIR absorption spectra. These results suggest a substantial decrease of the weakly bound nitrogen and carbon dangling bonds. Electron diffraction measurements reveal the existence of polycrystalline C₃N₄ structures in films annealed at 700 °C in a vacuum. The XPS studies confirmed that these crystalline phases are composed exclusively of carbon and nitrogen.