Effect of nitrogen content in amorphous SiCxNyOz thin films deposited by low temperature reactive magnetron co-sputtering technique

Abstract

Amorphous silicon oxycarbonitride (SiCxNyOz) films have been deposited on Si substrates by low temperature reactive magnetron co-sputtering of silicon and graphite targets in mixed Ar/N2 atmosphere. Our studies are focused on the influence of nitrogen incorporation on deposition rate, film composition, film structure, chemical bonds, and electrical resistivity of SiCxNyOz films investigated by profilometry, Rutherford Backscattering Spectrometry (RBS), X-ray diffraction (XRD), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), and four-point probe method. RBS results show that all samples contain significant amounts of oxygen (up to 16at.%) which led to the formation of SiCxNyOz. Further, XPS results show that most of this oxygen is located in the film surface. With the addition of N2 gas in the plasma, the carbon, and nitrogen contents in the films increase. The increased carbon content is due to the contribution of chemically driven sputtering of the graphite target and the reduction of the sputtering rate of the silicon target owing to poisoning by nitrogen. Raman spectra suggest that the films contain amorphous phases and that the a-C clusters suffer a graphitization with increased N2 gas flow rate. The XRD analysis confirmed the amorphous structure of these films. According to the XPS analysis, the increase in nitrogen content leads to an increase in SiN and CN bonds, decreasing the SiC, SiSi, and CC bonds. Finally, the films electrical resistivity depends mainly on the nitrogen content, which makes it possible to obtain semiconductor or insulator SiCxNyOz films only by adjusting the N2 concentration in the gas phase during the deposition process.