An apparatus for polishing a wafer comprises a supporting portion having an abrasive pad disposed thereon, and a polishing head disposed over the abrasive pad. The polishing head comprises a carrier having at least two fluid passages, a retainer ring disposed on a lower edge of the carrier, forming a...http://www.google.se/patents/US7223158?utm_source=gb-gplus-sharePatent US7223158 - Method for polishing a semiconductor wafer
