Appeal No. 2005-1011 Page 10
Application No. 09/921,588
flow and pressure to the outer perimeter of pad 16 relative to the center of pad 16. The
result of uneven fluid delivery is to accumulate more fluid (or slurry) at the perimeter of
the wafer rather than at the center to offset possibly greater abrasive force of an arcuate
pad applied at the center as shown. It is believed that by directing slurry with sufficient
force at the out perimeter of the wafer, more wafer will be removed at those perimeter
positions and relatively little slurry forwarded at the center of the wafer. The fluid
delivery non-uniformity is shown in Figure 2 to offset the abrasive pad-wafer contact
nonuniformity.
Figure 3 illustrates instances where pad 16 may not necessarily bow upward if
minimal polish pressure is applied through pad 16. This is contrary to that shown in
Figure 2. Instead, pad 16 maintains a relatively planar upper surface when brought to
bear against a wafer. It might be desirable in many instances to apply more fluid to the
center of the wafer then at the perimeter. Vectors 50 illustrate fluid flow and pressure
differentials. The fluid flow and pressure differentials may be selected to remove more
surface material at the center of the wafer, with gradual decrease as radial position
extends to the perimeter of the wafer.
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