Ion distribution functions in an Ar-Cl ECR discharge

Abstract

In processing plasmas, the ion distribution functions are generally non-Maxwellian and spatially varying. We have used the NRL axisymmetric particle simulation code QUASI-rz to calculate ion distribution functions at various positions in the plasma, for an ECR discharge in Ar/Cl gas mixture. We show that the distribution functions are determined by an interplay of several processes: ion acceleration due to the diverging magnetic field, or to the pre-sheath electric field, charge-exchange collisions, and Coulomb collisions between ions. Omitting any of these processes from a model radically alters the conclusions.

Limits of validity for orbital-motion-limited theory for a small floating collector

“…where n 0 is the ambient plasma density, T e is the electron temperature, and T i is the ion temperature. In laboratory discharges, T i T e within the bulk plasma, but T i /T e increases toward order unity at the bulk-sheath interface (Lampe et al 1998;Joyce et al 2000). We shall assume throughout this paper that a/λ D 1 and T i /T e < 1.…”

Two-dimensional simulation of an electron cyclotron resonance plasma source with power deposition and neutral gas depletion

“…Considerable effort has been made around this topic. For example, Joyce and et al [5] presented a model to investigate ion distribution functions with a self-consistent ECR heating. Yasaka et al [6] developed a self-consistent model of ECR plasma where two-dimensional profiles of the microwave electric field have been calculated by solving wave equation using the finiteelement method.…”

“…Yasaka et al [6] developed a self-consistent model of ECR plasma where two-dimensional profiles of the microwave electric field have been calculated by solving wave equation using the finiteelement method. But in these previous publications [4][5][6][7][8], the neutral gas density is a uniform distribution determined only by the applied pressure. In this work, both the assumptions are removed by incorporating the power absorption calculation based on the solution of the Maxwell equations and a balance model for the neutral gas density.…”

“…Recent progress along these lines has been impressive and much more effort has been made to develop computer simulation models of ECR plasma sources. The kinetic model [4], the fluid models [5,6] and the hybrid model [7][8][9][10] in one or two dimensions have been presented sequentially. This paper discusses not only the change of plasma parameters such as plasma density and ionization rate with operation conditions, but also ion angle distribution function at the substrate surface in an extended ECR plasma source.…”