Method for adaptive feedback controlled polishing

摘要

An adaptive feedback control method is provided for a chemical mechanical polish process to minimize a dielectric layer clearing time difference between two annular regions on a substrate. An optical system with an optical window passes below the polishing pad and detects reflected light interference signals from at least two annular regions. A pre-clearing time difference is determined and is used to calculate an adjustment to one or both of a CMP head membrane pressure and a retaining ring pressure. The pressure adjustment is applied before the end of the polish cycle to avoid the need for a second polish cycle and to reduce a dishing difference and a resistance difference in a metal layer in the at least two annular regions. In some embodiments, a second pressure adjustment is performed before the end of the cycle and different CMP head membrane pressure adjustments are made in different pressure zones.

主权项

1. A chemical mechanical polish (CMP) adaptive feedback control method, comprising:
(a) monitoring removal of a dielectric layer from a front side of a substrate during a CMP process by using an optical end point system, the front side of the substrate faces a polishing pad during a polish cycle while a substrate backside adjoins a CMP head membrane and is held in position by a retaining ring, the CMP process also removes a top portion of a metal layer that is within the dielectric layer and below a top surface of the dielectric layer; (b) determining a pre-clearing time of the dielectric layer removal for at least two annular regions on the substrate by collecting a reflected light interference signal from a first annular region at a first time (t1) after a polish cycle start time (tS), and collecting a reflected light interference signal from a second annular region at a second time (t2) after tS, the dielectric layer is formed on a metal etch stop layer in regions adjoining the top portion of the metal layer and the reflected light interference signal is comprised of light reflection from the dielectric layer and the metal etch stop layer in the regions adjoining the top portion of the metal layer; (c) calculating an adjustment to one or both of a retaining ring pressure and a CMP head membrane pressure that will minimize a clearing time difference between the first and second annular regions at an end of the polish cycle; (d) applying the adjustment to one or both of the retaining ring pressure and the CMP head membrane pressure during the CMP process; and (e) completing the polish cycle when a final portion of the dielectric layer is removed such that a top surface of the metal etch stop layer is coplanar with a top surface of the metal layer on the substrate.