Ignition process of a pulsed capacitively coupled RF plasma with a dielectric layer on a powered electrode

The temporal evolution of 2D spatial distribution of plasma parameters during ignition process of a pulse-modulated capacitively coupled plasma with a dielectric layer (with different heights) on a step-like powered electrode is investigated via a voltage and current probe and time-resolved optical emission spectroscopy. It is found that the presence of the dielectric layer on the powered electrode reduces the current growth rate and suppresses the overshoots in the OEI and power deposition, delaying plasma ignition. The height of the dielectric layer significantly affects the 2D distribution of the electric field as well as the electronic excitation rate, due to charge accumulation and partial voltage drop across the dielectric layer. For each height of the dielectric layer, the plasma ignition always occurs earlier above the metal part, due to a lower breakdown electric field between the electrode spacing. When the dielectric layer is lower the metal part, an OEI maximum is observed around metal edge, due to enhanced electric field. For the case of a higher dielectric layer, an OEI maximum is also present at the corner close to the metal-dielectric interface, due to enhanced electron power absorption by the horizontally expanding sheath of dielectric surface. The dielectric layer on the powered electrode can be used to model real scenario when a focus ring is present in the industrial plasma source, so the finding is expected to provide a better understanding of electron dynamics in a similar scenario.