| CPC B24B 37/32 (2013.01) [H01L 21/68721 (2013.01)] | 7 Claims |

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1. A retaining ring comprising:
an annular body including
a top surface configured to be secured to a carrier head;
a bottom surface configured to contact a polishing surface;
an outer surface extending from the top surface at an outer top perimeter to the bottom surface at an outer bottom perimeter; and
an inner surface extending from the top surface at an inner top perimeter to the bottom surface at an inner bottom perimeter, the inner surface comprising a plurality of regions spaced angularly around the annular body, wherein the plurality of regions comprise at least first regions and second regions, wherein each of the first regions is tilted at a first tilt angle with respect to the bottom surface, wherein each of the second regions is tilted at a second tilt angle with respect to the bottom surface, and wherein the first tilt angle is different from the second tilt angle.
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