Investigation of the power coupling efficiency in inductive discharges with radio-frequency substrate bias: dynamics of excitation and ionization patterns

Inductive discharges with a radio-frequency substrate bias are widely used in the field of materials processing. This is in particular true for fabrication of microelectronic devices where high plasma densities in combination with energetic ion bombardment of the substrate are required. Recently, it has been experimentally shown by Berger et al. (Appl. Phys. Lett. 111, 201601, 2017) that for distinct phases between the inductive (13.56 MHz) and the capacitive (27.12 MHz) input power, energetic beam electrons generated by the expanding boundary sheaths are well confined, are accelerated efficiently, and propagate vertically through the skin layer at the instants of time of maximum azimuthal induced electric field within the fundamental RF (13.56 MHz) period. It has been shown that this in fact enhances the inductive stochastic electron heating, the power coupling efficiency, and finally the ion flux toward the substrate. We investigate this phenomenon (observed experimentally in argon and neon gas) computationally by using the Hybrid Plasma Equipment Model (HPEM) developed by Mark Kushner. Furthermore, first results in more complex and process-relevant plasmas are presented.