Electron Cyclotron Resonance In a Weakly Magnetized Inductively Coupled Plasma with a DC-Biased Grid*

Electron cyclotron resonance (ECR) in a weakly magnetized inductively coupled plasma with a DC-biased grid is investigated. The electron temperature decreases at the region below the negatively biased grid. At low pressures, when magnetic field is applied, ECR occurs at both regions of the grid. Interestingly, in Ar plasma, the ECR effect is still observed in the region below the grid, even at 50 mTorr. This phenomenon can be explained by the Ramsauer effect of argon gas. When the electron temperature approaches to the electron energy of Ramsauer minimum(~0.1 eV), as electrons collide less with neutral gases, electrons can be continuously heated while gyrating along the magnetic field line even at high pressures. At the region above the grid, the ECR disappear as the pressure increases, since Ramsauer effect is not dominant because of high electron temperature. Also, at He, the non-Ramsauer gas, the ECR does not occur at high pressures below the grid.