Neutral Particle and Plasma Density Distributions in a Processing Plasma Source

Abstract

Neutral particle and plasma density distributions in a plasma source are calculated by solving the diffusion equation. Although the boundary condition n=0 at the wall is often used, it is not necessarily correct for practical plasma sources. We have used boundary conditions in consideration of the influxes into the wall; the densities at the wall are not zero. The distributions of neutral and plasma particles are expressed by the same formula. We can then compare those distributions by using the same formula. Some calculated examples are shown. The distributions at the target wall depend on the conditions at the side wall of the source and the initial distributions upstream of the source. By optimization of these conditions and the initial distributions, wide uniform distributions at the target wall can be obtained over a wide pressure range. The formulas are useful for the design of a plasma source.