Composition and chemical structure characteristics of CNx layers prepared by different plasma assisted techniques

Abstract

CNx layers were grown on Si (100) wafers and cleaved NaCl (100) slices by reactive sputtering of graphite in DC nitrogen plasma, by DC and RF magnetron sputtering of graphite in N2 or N2+Ar mixture, and from C-containing precursors in nitrogen by plasma-enhanced chemical vapour deposition (PECVD). The chemical structure of the deposited layers was characterised by XPS and FT-IR spectroscopy. DC plasma deposition resulted in layers with high N content, close to CN stoichiometry (x≈1), as determined by XPS. The CNx layers deposited by DC or RF magnetron sputtering contained 22–32 at.% N (x≈0.3–0.5). For layers prepared by PECVD, N-content varying between 20 and 50 at.% was characteristic. The broad and asymmetric C1s and N1s XPS spectral lines manifested several chemical bonding states of the constituents. The proportions of the line components varied with the preparation conditions. Significant differences were also observed in the 1100–1700 cm−1 region of the FT-IR spectra. Assignment of the two major N1s photoelectron peak-components was proposed based on the established correlation between the FT-IR results, composition and binding energy values measured for magnetron-deposited CNx phases as follows: the N1 at 398.3 eV BE to NC double bonds and N2 at 400.2 eV BE to NC single bonds.