J. Coppeta et al., Investigating slurry transport beneath a wafer during chemical mechanical polishing processes, J ELCHEM SO, 147(5), 2000, pp. 1903-1909
In order to better understand the role of thr fluid behavior in chemical me
chanical planarization, we measured slurry transport beneath a glass wafer.
We quantified the slurry transport using residence time distribution techn
iques and two measures of slurry transport efficiency, defined as the perce
ntage of new slurry beneath a wafer. Slurry transport efficiency depended o
n platen speed, flow rate, and the conditioning method. We found that the a
verage fluid residence rimes under the wafer decreased roughly linearly wit
h platen speed, A threefold increase in platen speed decreased slurry mean
residence time by a factor of 3.5. Changing the flow rate from 20 to 50 mL/
min decreased the slurry mean residence times by 80%. In situ conditioning
generally increased the slurry mean residence times and the amount of slurr
y mixing. In situ conditioning also decreased gradients in the slurry compo
sition across the wafer. Pad topography had a large effect on the slurry gr
adients that developed across the wafer. Finally, we found that the slurry
mixing history can he accurately modeled using a simple continuous function
. (C) 2000 The Electrochemical Society. S0013-4651(99)05-005-3. All rights
reserved.