Experimental Observation of Electron Density Increase below a DC-biased Grid in a Weakly Magnetized Inductively Coupled Plasma

The effect of a DC magnetic field on electron density is investigated in an inductively coupled plasma with a DC-biased grid. When the grid is negatively biased, electrons are accelerated through the grid sheath, resulting in the generation of secondary plasma below the grid. Interestingly, as the magnetic field (>25 G) increases, the electron density at the center decreases by up to 30% above the grid, while it increases by nearly a factor of 20 below the grid. This contrasting behavior is attributed to electron confinement that depends on electron temperature. Furthermore, the threshold magnetic field required to initiate the increase in electron density below the grid shifts to higher values as the grid bias becomes more negative, indicating a strong interaction between electric and magnetic field effects. These results provide insight into electron behavior in weakly magnetized plasma with the grid system and may help improve process control in semiconductor manufacturing.