O₂ rf discharge structure in parallel plates reactor at 13.56 MHz for material processing

The spatiotemporal structure of O₂ rf discharges between parallel plates at 13.56 MHz is investigated by using the relaxation continuum model. The results for pressure of 0.5 Torr and the sustaining voltage of 75-200 sin ωt V are studied by considering the elementary particles, O ⁺₂, O⁺, O^-₂, O ^-, electrons, and O in O₂. In these conditions, atomic oxygen, formed by the dissociative electron impact in O₂ with density of ∼10¹⁴ cm^-3, plays important role to the rf structure through the associative detachment process. That is, the expanding characteristics of the sheath width unique to the O₂ rf discharge are realized with increasing the sustaining voltage. The validity of the numerical result is demonstrated with the spatiotemporal structure by the measurement by the spatiotemporally resolved optical emission spectroscopy. The flux of each particle to the electrode is also discussed.