Patent ID: 6893327

Claim:
A polishing head for polishing a surface of a substrate against a polishing pad surface to achieve an even removal of material near the substrate surface edge and interior to the substrate surface edge, the polishing pad surface having a hardness and undergoing a deformation when a pressure force is applied and having at least a partial rebound from the deformation in a first time period after a portion of the pressure force is removed and having a full rebound in a second time period after all the pressure force is removed, the polishing pad being viscoelastic so that it exhibits different elastic properties to force applied in different directions or for different lengths of times and having a thickness that changes over time, the polishing head comprising: a carrier; a subcarrier carried by the carrier and adapted to hold the substrate during a polishing operation; and a retaining ring having an inner edge disposed about the subcarrier and a lower surface in contact with the polishing surface during the polishing operation, the lower surface of the retaining ring having at least one recess disposed along a substantially annular path on the lower surface of the retaining ring and sized in width and depth so that the polishing pad surface adjacent the recess at any moment during polishing partially rebounds an amount of the polishing pad into the recess so that the polishing pad surface fully rebounds in a shorter time and in a shorter distance after moving under the substrate across the inner edge of the retaining ring, the force on the substrate in an area near the outer edge of the substrate being thereby adiusted to achieve a predetermined polishing effect where the amount of material removed from the substrate surface edge is substantially the same as the amount of material removed interior to the substrate surface edge, the at least one recess positioned a predetermined distance from the inner edge of the retaining ring, selected based on a magnitude of a first force applied to the retaining ring during the polishing operation, a magnitude of a second force applied to the subcarrier during the polishing operation, or both.