Retaining ring structure for edge control during chemical-mechanical polishing
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United States of America Patent
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Apr 18, 2006
Grant Date -
Mar 2, 2006
app pub date -
Aug 31, 2004
filing date -
Aug 31, 2004
priority date (Note) -
Expired
status (Latency Note)
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Abstract
The retaining ring has a plurality of slurry channels wherein each alternate channel is recessed away from the inner circumference of the pad contacting surface forming a recess which extends upward from the bottom surface sufficient to prevent contact of the retaining ring with the polishing pad. Each recess curves towards the inner circumference of the retaining ring in a manner to form a rounded tab, tangent to the inner circumference of the retaining ring, and meeting the inner circumference at the exit end of an adjacent non-recessed slurry channel. The total effective contact length of the ring with the wafer edge is about one-tenth of the wafer perimeter. This is sufficient to properly contain the wafer during polishing and provides a large area of undistorted polishing pad at the wafer edge. By adjusting the operating pressure of the polishing head, it is possible to obtain polishing rates at the wafer edge which are larger or smaller than the overall wafer polishing rate.
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