Effect of helium on spatial plasma parameters in low pressure argon-helium plasma

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

“…3. Interestingly, with a further increase in the helium gas proportion (80% of the mixing ratio of helium gas), the EEPF transitioned to the biMaxwellian distribution, which was a characteristic representing non-local electron kinetics [14,20], as shown in Fig. 3.…”

“…Druyvesteyn-like distribution [14], even though the argon gas pressure was as low as 5 mTorr. This is quite different to other studies where the EEPFs had a Maxwellian or bi-Maxwellian distribution [19][20][21][22][23], because a lower driving frequency (400 kHz) than the conventional radio frequency (13.56 MHz) was used in this work.…”

“…In the pure argon discharge, the distribution profile was a concave type with a maximum at the radial edge. However, by adding helium gas, the concave profile became flat, which generally infers uniform plasma density [14].…”

“…In the ferrite-core side type ICP, Bang et al observed the change in the plasma density profile with diluted He gas in Ar ICP because of the different electron heating and collision process [14]. However, the spatial electron temperature, plasma potential distributions and related physical mechanisms were not studied.…”

“…center of the chamber [14]. This change in the ionization process at the center can introduce variation to the plasma potential, which is usually maximized at the center of the chamber in the non-local kinetics regime.…”