3-DIMENSIONAL OPTICAL-EMISSION TOMOGRAPHY OF AN INDUCTIVELY-COUPLED PLASMA

The three dimensional distribution of the net production rate of excit ed species in an inductively coupled plasma (ICP) reactor in Ar has be en measured as a function of pressure and discharge power. The ICP rea ctor is driven by a single turn radio-frequency current coil at 13.56 MHz. Robot assisted optical emission tomography was used in order to o btain radial profiles of emission at different distances from the coil thus giving effectively a three dimensional distribution of the net e xcitation rate as well as the number density of excited states. Under some conditions azimuthal symmetry of the discharge is broken mostly a t higher pressures and higher powers. We have covered a range of press ures between 15 and 500 m Torr and powers between 50 W and 400 W. The conditions for producing a uniform distribution of excited atoms as a representative of active species, are discussed.