Effect of target self-bias on carbon nitride thin films deposited by RF magnetron sputtering

Analysis of carbon nitride films (CNx) deposited by RF magnetron sputtering on crystalline silicon, under different target self-bias, is reported. The properties of films were determined in their as-deposited state using X-ray photoelectron spectroscopy (XPS), IR absorption, transmission spectroscopy and residual stress measurements. The presence of various types of C–N bonds, as well as of hydrogen and oxygen, is revealed. A good correlation is observed between the variation of N/C ratio, the optical gap E04 and the internal stress as a function of the target bias. The optical gap E04 decrease is discussed in terms of N/C ratio evolution, the sp2 bond content and the local distortions of the sp2 bonds.