Low energy electron heating and evolution of the electron energy distribution by diluted O2 in an inductive Ar/O2 mixture discharge

A remarkable increase in electron temperature with diluted O2 gas was observed in a low pressure Ar/O2 mixture inductive discharge from the measurement of the electron energy distribution function (EEDF). At a pure Ar gas discharge of 3 mTorr and 100 W, the measured EEDF had a bi-Maxwellian distribution with two electron temperature groups. However, as the O2 flow rate increased with fixing total gas pressure, a significant increase in the low energy electron temperature was observed. Finally, the EEDF evolved from a bi-Maxwellian to a Maxwellian distribution. These results can be understood by an efficient low energy electron heating from both an enhanced collisionless and a collisional heating mechanism because of increases of both skin depth and the elastic collision with the non-Ramsauer gas, O2. These experiments were also studied with different ICP power and Ar/He mixture.