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

Abstract

Production 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. Highdensity nitrogen plasmas with densities of 4 x 10(exp 12) cm(exp -3) were obtained in nitrogen at nitrogen pressure of approximately 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, showing that a high concentration of atomic nitrogen was produced in the high-density plasmas. This is different from the spectra measured for the induction-mode (non-wave excitation) low-density plasma dominated by the molecular band emission associated with the first positive system of N2, which is likely to be the case with conventional plasma sources. 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. Compositional characterizations with Rutherford Backscattering Spectrometry (RBS) showed that the N/C ratio of approximately 1.3 was achieved by depositing the CN films at plasma densities as high as 1 x 10(exp 12) cm(exp -3), where the line emissions of atomic nitrogen were significantly higher than the molecular band emissions. The increase in the plasma density and/or in the ratio of the atomic nitrogen (NI) emission intensity to the molecular band in the vicinity of the substrate were found to directly affect the N/C ratio in the CN films.