A Sectional Model for Investigating Microcontamination in a Rotating Disk CVD Reactor

Abstract

A sectional model is employed to study the aerosol dynamics in a rotating disk CVD reactor. The aerosol model is implemented into a numerical code that employs detailed chemistry and transport and a one-dimensional similarity transform to simulate this system. The numerical results are compared to experimental data where conditions are such that particles are formed from gas-phase reactions. A thin particle layer is reproduced and the thickness is accurately determined. The location of the layer is predicted within 5%. The thin layer is a consequence of the particle stagnation region that develops due to convection towards the disk being opposed by a particle thermophoretic velocity away from the disk. The effect of sticking coefficient is examined, and it is shown that with a small sticking coefficient a smaller mean particle size and broader particle layer is obtained. It is also found that particle layers are driven farther away from the disk when the temperature of the disk is higher or the chamber pressure is lower, both of which result in higher thermophoretic velocities for the particles. The thickness of the particle layer is found to be insensitive to pressure. The sectional model also reveals that the particle size distributions are bimodal throughout most of the particle layer. This is a result of the broad regions for nucleation and surface growth as well as the opposing convective and thermophoretic velocities.