Diagnostic measurements on a dense hollow cathode arc deposition plasma

Abstract

A hollow cathode arc plasma is used for the deposition of amorphous hydrogenated carbon (a-C:H) and aluminum-carbon (AI/a-C:H ) films. Gas flow rates are 40 sccm Ar or 120 sccm He. The arc power is of the order of 1 kW and the chamber pressure 0.1–1 Pa. As reactive gases, CH 4 or C 2H 2 are added at rates of 2–5 sccm, and in some experiments, Al is effused into the plasma. The plasma was analyzed using Langmuir probe measurements and energy dispersive mass spectrometry. From the probe measurements, electron temperatures of the order of 7–10 eV and densities of the order of 10 11–10 12/cm 3 were determined. Mass spectra indicated CH 3 + and C 2H 2 + ions as the most abundant ionic hydrocarbon species in argon-methane and -acetylene deposition plasmas, respectively. The ion energy distribution functions (IDF) of the various ions arriving at a grounded substrate were measured. It appeared that the main part of each function is a distribution centred around an energy corresponding to the plasma potential, that is about 20 eV. The measured energy spectra were simulated numerically by means of a one-dimensional plasma-sheath model.