The electromagnetic basis of the transformer model for an inductively coupled RF plasma source

An air-cored transformer model is commonly used to analyse macroscopic measurements of the electrical properties of inductively coupled, H-mode RF discharges. In this paper, we explicitly expose, via an electromagnetic theory of the H-mode plasma produced within a planar coil ICP, the manner in which the values of the circuit elements of the transformer representation are related to the values of the electron number density and effective collision frequency of the generated plasma. A comparison of experimental measurements and theoretical predictions lends credence to the view that the transformer model of H-mode discharges has a very useful role to play in the design and understanding of inductively coupled RF plasma sources.