AVS 46th International Symposium
    Manufacturing Science and Technology Group Monday Sessions
       Session MS-MoM

Paper MS-MoM6
Characterization of Showerhead Performance at Low Pressure

Monday, October 25, 1999, 10:00 am, Room 611

Session: Advanced Design Methodologies and Factory Modeling
Presenter: D.B. Hash, ELORET
Authors: D.B. Hash, ELORET
T. Mihopoulos, Motorola Inc.
M. Meyyappan, NASA Ames Research Center
D.G. Coronell, Motorola Inc.
Correspondent: Click to Email
The overall objective of this work is to characterize the flow through showerheads by deriving pressure drop versus velocity correlations that can be then used in reactor scale simulations where the showerhead is approximated as a porous medium. At relatively low Reynolds numbers (< 1-10 based on the hole length scale) and in the absence of slip flow, Darcy's Law, gradient P = µ U/ k, can be used to express the relation between the pressure drop and velocity where µ is the fluid viscosity and k is the permeability that can be theoretically predicted as k = e R@super 2@ /8, where e is the porosity. However, at sufficiently small hole diameters and decreased pressures (< 5 Torr), the Knudsen number based on showerhead tube radius increases, and the flow may be in a transition regime. Different expressions have been proposed to account for this effect in the permeability by expressing k as a function of either pressure or Knudsen number. But at even higher Knudsen numbers, the pressure drop - velocity dependence is non-linear, and Darcy's Law no longer holds such that a permeability cannot be defined. The direct simulation Monte Carlo method is used along side conventional CFD techniques to determine the extent to which the CFD technique is appropriate and helps to derive correlations for the more rarefied cases of interest in these showerhead flows.