Theoretical overview of the large area plasma processing system (LAPPS)

An experimental and theoretical study of LAPPS has been underway at the Naval Research Laboratory for about a year now. LAPPS is plasma produced by a sheet electron beam guided by a magnetic field through a background gas. Typical parameters are several kilovolts and tens of milliamps per cm2 for the beam, a field of order 100 G, and a background pressure of order 100 mtorr, and an electron density of 1012 cm-3. The plasma size is approximately one meter square by 1 cm thick. By placing a substrate adjacent to the plasma, large areas can be treated by the plasma. LAPPS has several potential advantages for plasma processing including large area, high uniformity, high electron density good control of ion and free radical flux to the substrate, and very efficient production of ions and free radicals. An initial theoretical study of LAPPS has focused on plasma and free radical production, ion fluxes to substrates, uniformity of the plasma and flux for insulating and conducting substrates, as well as dc and rf sheaths. This theoretical work has been used to analyze several initial experiments on isotropic etching, ion fluxes to conducting substrates, and measurements of electron temperature.