Operating regions and transitions for low-pressure inductively coupled oxygen plasmas

Summary form only given, as follows. An inductively coupled radio-frequency oxygen discharge is investigated based on various diagnostic tools. Experimental measurement is performed at a range of gas pressure 1-30 mTorr, and RF power of 100-1000 W. In electronegative discharge such as oxygen plasma, the parameter space of pressure and absorbed power can be divided into volume recombination loss-dominated region and ion-flux-loss dominated region according to prevailing loss mechanism. The scaling relations for densities of charged particles in terms of the plasma parameters are experimentally investigated at both regions. The electronegativity and the shape of spatial profiles of charged particles also depend on the operating region in the parameter space. These characteristics associated with various operating regions and the transitions between the operating regions with varying control parameters are investigated by probing the major plasma parameters with techniques such as plasma induced optical emission spectroscopy, electrical measurement of RF current and RF voltage, and Langmuir probes. The emissions at 777 and 845 nm from excited oxygen atom are chosen for the optical detection. In the Langmuir probe diagnostics, the negative ion temperature and the negative ion density are estimated based on the test function method. The experimental results from the various diagnostics tools confirm the validity of the classification of the operating regions and show the transitions between them clearly.