Excitation Mechanisms and Sheath Dynamics in Capacitively Coupled Radio‐Frequency Oxygen Plasmas

Phase resolved optical emission spectroscopy (PROES) was used to determine the spatio‐temporal behavior of excitation rates in rf sheaths of capacitively coupled plasmas at 13.56 MHz. The plasmas were ignited in pure oxygen at pressures from 20 to 100 Pa and rf powers from 10 to 100 W. The spatial and phase resolved excitation rates have shown four characteristic patterns, which differing in their spatial and temporal position. PIC‐MCC simulations of the oxygen capacitively coupled radio‐frequency discharge were used to get a detailed microscopic description of the dynamic processes in rf plasmas. The PIC‐MCC simulations reproduced the excitation patterns observed in experiment quite well and allowed to identify the underlying physics. Three excitation patterns appearing in front of the powered electrode were found tobe due to electron impact dissociative excitation of molecular Oxygen, whereas the fourth pattern very close to the powered electrode is attributed to collisions of the positive ions with the background gas (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)