Development of highly reactive high-density plasma sputtering process with excitation of helicon wave for synthesis of superhard nitride films

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We performed investigations on the helicon-wave excited nitrogen plasmas generated using the m=0 mode helical antenna, which was designed for the reactive sputter synthesis of superhard nitride films. The achieved plasma density in m Torr range of nitrogen gas was measured to be 1012〜1013 cm-3. Carbon nitride films were deposited by the reactive sputtering of carbon target with the helicon waveexcited high-density nitrogen plasmas. Compositional characterizations of the CN films showed that the N/C ratio of〜1.3 was achieved by depositing the CN films at plasma densities as high as lx1012 cm-3. Increase in the plasma density and/or the emission-intensity ratio of the atomic nitrogen 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 showed that the bonds associated with hydrogen impurity could be effectively eliminated by increasing the substr … More ate temperature rather than intense UV light irradiation during film growth. Nanoindentation measurements showed that the hardness values of as high as 〜20 GPa was attained. We also performed investigations on the RF circuit configurations and the discharge characteristics of internal type antennas for plasma sputtering. The RF voltage amplitude of the antenna conductor was shown to be minimized to 1/2 of the antenna terminal voltage when the impedance balance condition was met in the floating antenna regime. Furthermore, materials investigations on the stress relaxation for enhancement of the superhard nitride films were additionally performed by ion bombardment processes. Tribological and structural characterizations of the buffer layer indicated that the buffer layer control can be effective for stress relaxation, however, the peak shifts of the IR TO-phonon mode of cBN indicated the accumulation of the compressive strain with increasing film thickness could not be avoided in the superhard film growth using ion bombardment. Less