Observation of the transition of operating regions in a low-pressure inductively coupled oxygen plasma by Langmuir probe measurement and optical emission spectroscopy

In inductively coupled low-pressure oxygen plasmas, planar Langmuir probes were used to determine the variation of the plasma parameters (positive and negative ion densities, electron density, electron temperature) with appli ed pressure (1-40 mTorr) and power (1-800 W). Simultaneous optical emission spectra were obtained. The relative abundance of the species was estimated from the intensities of the two spectral lines from excited oxygen atoms a nd molecular oxygen ions. In conjunction with the Langmuir probe data, the scaling behaviours of the charged and neutral species were investigated. A change of scaling behaviour in charged and neutral species densities which was due to the transition from the ion-flux-loss-dominated region to the re combination-loss-dominated region was observed by Langmuir probe measuremen t and optical emission spectroscopy.