PLASMA TRANSPORT AROUND DUST AGGLOMERATES HAVING COMPLEX SHAPES

Dust particles generated in low temperature plasmas as used for microe lectronics fabrication are often agglomerates of smaller monodisperse particles. The transport of these agglomerates, and the subsequent con tamination of surfaces, depends on the details of ion-momentum transfe r (ion drag) to, and electrostatic forces on, the agglomerate. Given t hat the charge distribution on the surface of the agglomerate and loca l electric fields in the vicinity of the agglomerate depend on its sha pe, the subsequent forces on the agglomerate will also be a function o f shape. In this article, we describe results from a simulation in whi ch plasma transport around, and the charging of agglomerates are inves tigated. We find that the charge distribution on the agglomerates is g enerally nonuniform, a consequence of both shadowing and charge deplet ion. The ion-momentum transfer cross section, calculated using a Monte Carlo simulation, also depends on the shape of the agglomerate. (C) 1 998 American Institute of Physics. [S0021-8979(98)04711-2].