Ionization of sputtered carbon species by high-power inductively-coupled impulse sputtering (ICIS)

Abstract

A high-power inductively-coupled plasma (ICP) with a frequency of 160 kHz has been developed to sputter a target set nearby the plasma source. Argon ions were produced in the ICP and sputtered a graphite target. This system was called inductively-coupled impulse sputtering (ICIS). The sputtered carbon species were significantly ionized due to high-density argon ions on the order of 1019 m−3. An instantaneous coil power was about 27 kW and the average power was about 100 W. The target current density and the power density were about 1.3 A/cm2 and about 1.3 kW/cm2, respectively. Optical emission spectra of the plasma were observed, by which singly-ionized carbon ions were identified for wavelengths of 359.0, 387.6 and 392.0 nm. The emission intensity was changed by a voltage applied to the target although the observed wavelengths of the emission spectra were unchanged. It was seen that the carbon ions were limited near at the target. Electron impact collision and charge exchange would be dominant processes in the target plasma region. Temporal behaviors of the optical emission intensities of plasma species were studied. The intensity of the emission spectra is closely related to high-frequency coil current and the pulsed bias voltage.