Synthesis of carbon nitride films by high-density helicon wave-excited plasma sputtering

Properties of high-density nitrogen plasmas with excitation of the m=0 mode helicon wave has been studied for reactive plasma sputter synthesis of carbon nitride films. High-density nitrogen plasmas with densities of 4×1012 cm−3 were obtained in nitrogen at ∼0.1 Pa. Optical emission spectroscopy showed that the line emissions of atomic nitrogen (NI) and atomic-nitrogen ions (NII) were considerably enhanced in the helicon wave-excited high-density plasma, whereas, the spectra measured from the induction-mode (non-wave excitation) low-density plasma were dominated by those of the molecular band emission associated with the first positive system of N2. Carbon nitride films have been deposited on Si (100) substrates by reactive sputtering of carbon target with the helicon wave-excited high-density nitrogen plasmas at ∼0.1 Pa. Compositional characterizations of the CN films were performed using Rutherford backscattering spectrometry (RBS). The RBS analysis showed that the N/C ratio of ∼1.3 was achieved by depositing the CN films at plasma densities as high as 1×1012 cm−3, where the line emissions of atomic nitrogen were significantly higher than the molecular band emissions. Increase in the plasma density and/or the emission-intensity ratio of the atomic nitrogen (NI) to the molecular band in the vicinity of the substrate was found to directly contribute to the N/C composition ratio in the CN films. Structural analysis by Fourier transform infrared spectroscopy (FTIR) showed that the bonds associated with hydrogen impurity could be effectively eliminated by increasing the substrate temperature during film depositions.