Retaining ring for use on a carrier of a polishing apparatus
The invention provides a unitary retaining ring for use in a CMP apparatus. The retaining ring features a pad engaging surface which is designed to be flat and planar when the retaining ring is mounted to a carrier of the CMP apparatus. The pad engaging surface includes portions which surround the wafer and contact a pad and slurry on the CMP apparatus. A plurality of mounting features are provided along a carrier engaging surface of the ring. The mounting features are installed to cause localized compressive stresses in the material when in a demounted state. Upon mounting to a carrier of the CMP apparatus under specified torque or force conditions, tensile stresses are applied to the material of the ring resulting in a flat and planar mounted front surface.
1. A method of making a unitary retaining ring for use in a Chemical Mechanical Polishing (CMP) apparatus comprising the steps of:
forming a ring from a cylindrical or tubular plastic material;
machining inside and outside diameter dimensions to form inner and outer surfaces on the ring;
machining a planar carrier engaging surface on the ring between the inner and outer surfaces;
forming a plurality of mounting features on the carrier engaging surface in a manner causing a localized compressive stress in the area surrounding the mounting feature;
mounting the ring to a fixture which simulates the mount of a CMP apparatus;
machining a flat pad engaging surface on the ring between the inner and outer surfaces opposite the carrier engaging surface; and,
demounting the ring from the fixture.
2. The method of claim 1 wherein the mounting features are formed by first drilling holes into the carrier engaging surface and then inserting a reinforcing member in each hole.
3. The method of claim 2 wherein the retaining ring is mounted to the fixture by fasteners passing through holes in the fixture and secured to the reinforcing members of the mounting features causing a localized tensile stress in the ring.