Wafer de-chucking

Abstract

A carrier head ( 100 ) for a CMP tool, wherein the membrane ( 108 ) defining a chamber with a contact surface ( 102 ) of the carrier head ( 100 ) has a number of integral tubes ( 110 ) termining in openings coupled directly to the substrate ( 106 ), in addition to a main fluid flow passage ( 104 ) coupled to the chamber defined by the membrane ( 108 ). In use, during loading and polishing, a vacuum is applied to the main fluid flow passage ( 104 ) and the tubes ( 110 ) to hold the substrate ( 106 ) in flat engagement with the membrane ( 108 ) and contact surface ( 102 ). In order to unload the substrate ( 106 ), fluid pressure is applied to the substrate ( 106 ) via the tubes ( 110 ), whilst maintaining the application of the vacuum via the main fluid flow passage ( 104 ) so as to minimise bending and breakage of the substrate ( 106 ).

1 . A carrier head for a chemical mechanical polishing apparatus, the carrier head comprising a contact surface on which is provided a membrane for receiving a substrate to be polished, said membrane forming a chamber with said contact surface, the carrier head further comprising a main fluid flow passage coupled at one end to said chamber and at an opposite end to means for creating a vacuum or applying fluid pressure between said membrane and said contact surface, said membrane comprising at least one opening from which extends a respective fluid flow channel for selectively applying a vacuum or fluid pressure directly to said substrate, when in use. 
     
     
         2 . A carrier head according to  claim 1 , wherein the respective fluid flow channel that extends from the at least one opening in said membrane comprises an integral tube. 
     
     
         3 . A carrier head according to  claim 1 , comprising a respective guide passage for receiving the or each fluid flow channel. 
     
     
         4 . A carrier head according to  claim 3 , wherein the or each fluid flow channel is received within a respective guide passage in slidable engagement. 
     
     
         5 . A carrier head according to  claim 3 , comprising a plurality of concentric guide passages for receiving a plurality of respective fluid flow channels extending from respective openings in said membrane. 
     
     
         6 . A carrier head according to  claim 1 , wherein said main fluid flow passage is generally central relative to said contact surface and substrate and said one or more membrane openings and respective fluid flow channels are off-centre relative to said contact surface and substrate. 
     
     
         7 . A flexible membrane for use with a carrier head according to  claim 1 , for forming a chamber with said contact surface, the membrane comprising one or more openings from the or each of which extends a respective fluid flow channel. 
     
     
         8 . A method of performing chemical mechanical polishing in respect of a substrate comprising the steps of providing a carrier head according to  claim 1 , loading a substrate onto the contact surface said carrier head against said membrane, and applying a vacuum to said membrane via main fluid flow passage performing chemical mechanical polishing in respect of said substrate, and unloading said substrate by applying fluid pressure thereto via said at least one opening and respective fluid flow channel whilst maintaining the application of a vacuum to said membrane via said main fluid flow passage. 
     
     
         9 . A method according to  claim 8 , wherein during loading of said substrate, vacuum is additionally applied to said substrate via said at least one opening and respective fluid flow channel. 
     
     
         10 . A fluid pressure control system for performing the method of  claim 8 , in a carrier head according to  claim 1 , the fluid pressure control system comprising an outlet coupled to said main fluid flow passage and said one or more fluid flow channels and being configured to operate in a first, loading mode, wherein a vacuum is applied to said main fluid flow passage and said one or more fluid flow channels for loading said substrate onto said carrier head and performing chemical mechanical polishing in respect thereof, and a second, unloading mode, wherein a vacuum is applied to said main fluid flow passage and fluid pressure is applied to said one or more fluid flow channels for unloading said substrate from said carrier head.