Method and apparatus for controlled polishing

Abstract

An apparatus for controlling a polishing process, in particular for detecting an end point of the polishing process, comprising a rotating platen with a pad, a rotating head that supports an object to be treated, e.g., a semiconductor wafer, and performs radial movements with respect to the platen, and an end-point control system comprising a plurality of groups of various sensing devices for detecting an end point of the process. In the illustrated embodiment one group of the sensing devices is a group of electrical-conductive elements located on the surface of the pad and connected via contact pins embedded in the material of the platen to respective resistance measurement unit. A second group of sensing elements is represented by capacitance probes having conductive elements on the surface of the pad and connected via contacts embedded in the body of the platen to the capacitance measurement unit. A third group of sensing devices is represented by acoustic emission sensors built on various levels into components of the rotating head. A fourth group of sensing devices is represented by a pair of force/torque sensors connected with drive shafts of the rotating head and the platen, respectively, and intended for direct measurement of torques of respective shafts and a coefficient of friction between the wafer and the polishing pad. All groups of sensors work simultaneously and their measurement data is processed and analyzed by a control unit for obtaining accurate and reliable results.