Md. Oh et al., NUMERICAL-ANALYSIS OF PARTICLE DEPOSITION ONTO HORIZONTAL FREESTANDING WAFER SURFACES HEATED OR COOLED, Aerosol science and technology, 25(2), 1996, pp. 141-156
Numerical analysis was performed to characterize the particle depositi
on behavior on a horizontal freestanding wafer with thermophoretic eff
ect under the turbulent how field, A low Reynolds number turbulent k-e
psilon model was used to analyze the turbulent flow field around the w
ater. The deposition mechanisms considered were convection, Brownian a
nd turbulent diffusion, sedimentation, and thermophoresis, The average
d particle deposition velocities and their radial distributions for bo
th the upper and lower surfaces of the wafer were calculated from the
particle concentration equation in an Eulerian frame of reference, Whe
n the wafer is unheated, in the diffusion-controlled deposition regime
with particle size d(p) < 0.1 mu m the averaged particle deposition v
elocity under the turbulent flow was about 1.3 times higher than the l
aminar flow case, and the local deposition velocity near the center of
the wafer was high equivalent to that near the edge. The particle dep
osition on the lower surface was comparable to that on the upper surfa
ce, When heated, the deposition-free zone, where the deposition veloci
ty is lower than 10(-5) cm/s, exists between 0.096 mu m and 1.6 mu m w
ith Delta T of 10K, indicating shifting behavior to larger size range
compared with the laminar flow case. As for the local deposition veloc
ities, for d(p) < 0.05 mu m, the deposition velocity is higher near th
e center of the wafer than near the wafer edge, whereas for d(p)=2.0 m
u m the deposition takes place mainly on the inside area of the wafer.
The comparison of Phe present numerical results with the experimental
data by Ye et al. (1991) showed seasonably good agreement, Finally, a
n approximate deposition velocity model was suggested. The comparison
of the model calculations with the present numerical results and the e
xperimental data of Opiolka et al. (1994) showed good agreement.