| CPC B24B 37/26 (2013.01) | 19 Claims |

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1. A polishing head assembly for polishing of semiconductor wafers, the polishing head assembly comprising:
a polishing head having a recess along a bottom portion, the recess having a recessed surface; and
a cap positioned within the recess, the cap comprising:
an annular wall secured to the polishing head, the annular wall comprising a first portion having a first thickness and a second portion extending from the first portion and having a second thickness; and
a floor joined to the annular wall at a joint, the floor extending across the annular wall, the floor having an upper surface and a lower surface, the upper surface spaced from the recessed surface to form a chamber therebetween, wherein the first portion of the annular wall is joined to the floor and the first thickness is less than the second thickness to weaken a deformation resistance of a portion of the floor proximate the joint compared to other portions of the floor to allow the portion of the floor proximate the joint to deflect relative to the polishing head by a change of pressure in the chamber.
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