COMBINED EFFECTS OF THERMOPHORESIS AND ELECTROPHORESIS ON PARTICLE DEPOSITION ONTO A WAFER

A theoretical study of aerosol particles responding io thermophoresis and electrophoresis, and the deposition rate of the particles onto an axisymmetric wafer, is proposed. The flow is modeled as a two-dimensio nal, incompressible and steady-state laminar forced convective flow. T he mechanisms of particle deposition by convection, Brownian diffusion , sedimentation, thermophoresis and electrophoresis are coupled. Simil arity analysis is used to transform the governing equations for mass, momentum and concentration into a system of ordinary differential equa tions. Through numerical integration of the equation for particle conc entration, concentration profiles and deposition rates are obtained. W hile the results are compared with the simple-addition method for a on e-dimensional stagnant film model, the error on the film model increas es with an increase in the temperature gradient, particularly when the rmophoresis is the dominating mechanism. Comparing the experimental re sults from previous works with the calculated results of deposition ve locity, we find that the comparison shows a very good agreement. (C) 1 998 Elsevier Science Ltd. All rights reserved.