Patent ID: 7140956

Claim:
A chemical mechanical planarization apparatus comprising: a work piece carrier; a flexible work piece diaphragm having a substantially planar portion bounded by a periphery positioned in a plane beneath at least a portion of the work piece carrier; and at least one annular rib, the at least one annular rib comprising: a first end connected to the work piece carrier; a second end connected to the flexible work piece diaphragm; and a mid portion between the first end and the second end, the mid portion having a width dimension substantially less than a width dimension of the second end and wherein the at least one annular rib comprises an inner wall and an outer wall, each of the inner wall and the outer wall extending from the first end to the second end and wherein at least one portion of one of the inner wall and the outer wall is substantially perpendicular to the plane and a lower portion of one of the inner wall and the outer wall comprises a portion that is not perpendicular to the plane.