Measurement of the electron energy distribution function in CO2 inductively coupled plasma

Abstract

CO2 inductively coupled plasmas (ICPs) were generated using a radio frequency power of 13.56 MHz at 100 mTorr. Electron energy distribution functions (EEDFs) were measured using a single Langmuir probe, and various plasma parameters such as the electron density and electron temperature were obtained from the measured EEDFs. EEDFs with multislope structures are obtained. However, changes in the gas composition in the ICP were observed via optical emission spectroscopy. The electron density barely increases when a sudden change in the gas composition occurs. The E to H mode transition occurs at a stationary gas composition as the absorbed power increases. The EEDFs of CO2 plasma, CO plasma, and O-2 plasma were calculated using BOLSIG+, which is a two term Boltzmann solver [G. Hagelaar and L. Pitchford, Plasma Sources Sci. Technol. 14(4), 722 (2005)]. The measured EEDF is closest to the EEDF of the CO plasma.