Determination of the equivalent circuit of inductively coupled plasma sources

This article presents a new approach to investigate and model the electrical characteristics of inductive plasma sources. The technique is primarily based on the measurement of the total complex impedance of the plasma source. The measurements are subsequently numerically fitted to a generic and qualitative electrical model, predetermined by a classical Bode analysis of a circuit including a conductive dummy load of size comparable to the plasma itself. The match between the modeling and the experimental data using this new approach shows a drastic improvement compared to the usual inductively coupled plasma (ICP) electrical model, which is also detailed here as a comparison. We conclude the article on prospective benefits of an accurate electrical model for ICP plasma sources, showing in particular that the global electrical parameters of the discharge can be correlated with a good level of accuracy to the local electrical parameters of the plasma. Beyond the technological necessity to better understand the ICP plasma sources, these results also open many doors towards nonintrusive and accurate plasma monitoring technologies. (C) 1999 American Institute of Physics. [S0021-8979(99)09303-2].