Measurements of the spatially resolved electron temperature and plasma potential in ferrite-core side type Ar/He inductively-coupled plasmas

• Spatially resolved plasma parameters were measured by single Langmuir probe in ferrite core inductively coupled plasma.
• The evolution of measured EEPFs from Langmuir probe was supported by analyzing observed optical emission spectra.
• The electron heating mechanism was change from local to non-local by increasing helium partial pressure in argon discharge.

Spatial distributions of the effective electron temperature (Teff) and plasma potential were studied from the measurement of an electron energy probability function in a side type ferrite-core inductively coupled plasma with an argon–helium mixture. As the helium gas was diluted at the fixed total gas pressure of 5 mTorr in an argon discharge, the distribution of the plasma density and plasma potential changed from a concave to a flat profile, and finally became a convex profile, while all spatial profiles of Teff were hollow shapes with helium dilution in the argon discharge. This evolution of the plasma potential with helium gas could be explained by the increased energy relaxation length (λε), indicating the transition of electron kinetics from local to non-local kinetics.