Diagnostics of Inductively Coupled Chlorine Plasmas: Measurement of Cl sub 2 sup + and Cl sup + Densities

The absolute densities of the positive ions (Cl sub 2 sup + and Cl sup +) are obtained over a 2-20 mTorr pressure range and 5-1000 W input (radio frequency) rf power range in a transformer coupled Cl sub 2 plasma. The relative number density of Cl sub 2 sup + is measured by laser induced fluorescence. These laser induced fluorescence data are calibrated by Langmuir probe measurements of total positive ion density at low powers to yield absolute values for n sub (cl sub 2 sup +) and are corrected for changes in rotational temperature with rf power. 

In turn, the n sub (cl sub 2 sup +) data are used to determine the effective mass correction for refined Langmuir probe measurements of the total positive ion density. The density of Cl sup + is then the difference between the total positive ion and Cl sub 2 sup + densities. For all the pressures, Cl sub 2 sup + is found to be the dominant ion in the capacitively coupled regime (input powers below 100 W), while Cl sup + is the dominant ion at higher powers (> 300W) of the inductively coupled regime. 

Experimental results are compared to those from a simple global model. This work is a continuation of a study that provides a complete set of experimentally measured plasma parameters over a broad range of conditions in a chlorine plasma, produced with a commerical inductively coupled rf source.