Electrical and plasma characterization of a hybrid plasma source combined with inductively coupled and capacitively coupled plasmas for O atom generation

Abstract

We developed a hybrid plasma source combined with an inductively coupled plasma (ICP) antenna and a capacitively coupled plasma (CCP) electrode. The ICP antenna and the CCP electrode are connected to a single RF power generator in parallel and a variable capacitor Cv is connected to the ICP antenna in series. The currents flowing through each source and the CCP electrode voltage are measured for analysis of the electrical characteristics, and the ion densities are measured while adjusting the capacitance of the Cv. Interestingly, when a series LC resonance occurs between the inductance of the ICP antenna and the capacitance of the Cv, different trends are observed depending on the discharge mode. In capacitive mode (E-mode), the ion density is minimized and is controlled by the CCP current. On the other hand, in inductive mode (H-mode), the ion density is maximized and is affected by the ICP current. The change of the ion density can be explained by the balance between the total power absorption and power dissipation. It is also in good qualitative agreement with the calculated plasma density from the power balance equation. By adjusting the Cv, linear control of the ion density can be achieved. To evaluate the proposed source in terms of O atom generation, the number density ratio of O atom nO to Ar nAr is obtained by using the optical emission spectroscopy actinometry method. These results show that nO/nAr is controlled. Our source can be applied to plasma processing, in which ion density and O atom generation controls are important factors.