Criterion for Sheath Formation in Negative Ion Plasma with Electron Beam

Abstract

The criterion of sheath formation in a plasma containing negative ions have been investigated for the case with an injected electron beam. It has been found that at a constant negative ion density ratio the sheath edge potential and the positive ion flux increase with the relative electron beam density. From the balance between the flux of negative charged particles and the positive ion flux, the floating potential of a substrate immersed in the plasma is calculated based upon the above sheath theory. It has been found that the floating potential of an insulating substrate is variable with the relative electron beam and negative ion densities in a wide range. This means that in an etching plasma the substrate potential can be controlled by injecting a low density electron shower.