Particle transport modelling in semiconductor process environments

Abstract

We review our recent efforts to develop and apply computational models that can predict fluid, thermal and particle transport in semiconductor process equipment such as that used for chemical vapour deposition or plasma etching. The purpose of this work is to supply equipment designers and operators with models that allow them to optimize process conditions and to develop tool designs that reduce particle contamination levels. The algorithms for predicting particle transport are briefly described. A Lagrangian approach is used in this work when both particle inertia and applied forces are important, while a Eulerian approach is used when both particle Brownian motion and applied forces are important. As an example, a commercial finite-element code is used to calculate the fluid and thermal fields in a simple geometry representative of real single-wafer processing tools, namely axisymmetric flow between a showerhead and a parallel plate separated by a small gap. Using the calculated velocity field, both Lagrangian and Eulerian particle transport formulations give the same particle collection efficiency for terminal-velocity-dominated deposition when particle inertia can be neglected. Although plasma-induced forces on the particles are not treated in detail, we discuss how models for these forces can be incorporated into the Lagrangian and Eulerian framework as they become available.