Influence of electron beam on profile of sheath potentials in electron-beam-excited plasma apparatus

Abstract

A variety of plasma processes for the sake of new material fabrication and etching process has been attempted. In this research, the relationship between sheath potentials and electron energy distribution functions (EEDFs) in electron-beam-excited plasma (EBEP) apparatus is revealed, because the ion sheath surrounding substrates has become important in the plasma process. Hence, the potentials measured are compared with those calculated with two theoretical current balance equations at the sheath edge both in the EBEP region where processing plasma is produced by collision of electrons against reactive gas particles and in the electron-beam accelerating region where electrons are accelerated, substituting the experimental parameters into them. The results are summarized as follows. (1) In the EBEP region, monochromatic electron-beam current was assumed, and the potential profile depends on its kinetic energy at the sheath edge. (2) In the accelerating region, a finite-temperature beam current was assumed inside the electron beam, and the potential profile depends on its average kinetic energy and its spread , whereas the same result as in the EBEP region is obtained outside the beam. From these results, it is found that the electron beam has important roles in the determination of sheath potential in the EBEP apparatus. Namely, they suggest the advantage of controlling sheath potential in EBEP apparatus and the possibility of controlling it even in other apparatuses using an electron beam.