The influence of oxygen ratio on the plasma parameters of argon RF inductively coupled discharge

In this paper, the RF-coupled plasma characteristics of argon and oxygen mixed gases were analyzed by emission spectra and Langmuir single probes. The experimental pressure was kept at 0.63 Pa, and the electron temperature and electron density were measured by Boltzmann curve method and Langmuir single probe respectively under different oxygen ratio. The results demonstrate that increasing the oxygen content reduces the plasma electron density, and the plasma will change from E mode to H mode when the discharge power increase from 350 W to 400 W if the discharge gas is pure argon or oxygen ratio is low, but the plasma is in a single E-mode at relatively high oxygen ratios. When the power reaches 450 W, the plasma becomes unstable and the state of plasma will change no matter what mode it is (H mode or E mode). In addition, as the oxygen ratio increases, there is a good agreement between the plasma electron density and the argon 738.74 nm line intensity. However, the electron temperature will decrease in H mode.