Retaining ring for wafer polishing

Abstract

An improved wafer polishing machine is disclosed. In one embodiment, the wafer polishing machine has a movable polishing surface and a holder that holds an object, such as a semiconductor wafer, against the movable polishing surface. The holder includes a support structure that supports the object in contact with the polishing surface and an annular retaining ring that retains the object in alignment with the support structure. The retaining ring has a plurality of projections projecting inwardly from its inner circumference. The projections are evenly spaced around the inner circumference of the retaining ring. In one embodiment, the projections on the retaining ring define a circle with a diameter no less than the diameter of the object being polished. In an alternative embodiment, the retaining ring has a smooth, circular inner circumference formed from a flexible material which distends to from a continuous arc of contact with the wafer during polishing. Each retaining ring disclosed herein forms multiple points of contact or a continuous arc of contact between the retaining ring and the wafer, thereby reducing wafer buckling during polishing and improving surface uniformity.