Acoustic window in pad polishing and backing layer for chemical mechanical polishing

Abstract

Disclosed herein is a polishing pad includes a polishing layer, a backing layer, and an acoustic window extending through the backing layer and the polishing layer, wherein an upper surface of the acoustic window is coplanar with a polishing surface of the polishing layer and a chemical mechanical polishing apparatus including a platen; a polishing pad supported on the platen; a carrier head to hold a substrate against the polishing pad; a motor to generate relative motion between the platen and the carrier head so as to polish an overlying layer of the substrate; an in-situ acoustic monitoring system comprising an acoustic sensor coupled to the acoustic window to receive acoustic signals from the substrate; and a controller configured to detect a polishing transition point based on received acoustic signals from the in-situ acoustic monitoring system.