Measurements of electron energy distribution functions in pulse-modulated Ar and Ar/O₂ inductively coupled plasmas using laser Thomson scattering

The time-resolved electron energy distribution functions (EEDFs) in Ar and Ar/O₂ pulse-modulated inductively coupled plasmas have been measured in the afterglow for the first time using laser Thomson scattering. The measurements were performed for RF powers of 100 and 500 W at a frequency of 13.56 MHz, a duty cycle of 50%, and a pulse repetition frequency of 12.5 kHz. The Ar pressures were 20 and 100 mTorr at a flow rate of 132 seem, and the Ar/O₂ (10% O₂) pressure was 20 mTorr at a flow rate of 132 sccm. The measured EEDFs were all Maxwellian for the Ar and Ar/O₂ (10% O₂) plasmas. The Maxwellian distributions in the afterglow may be attributed to electron-electron collisions.