Chemical mechanical polishing apparatus with non-conductive elements

Abstract

Conductive elements of a chemical mechanical polishing system may generate undesired eddy currents under the influence of a time-dependent magnetic field used in an eddy current monitoring system. To improve the accuracy of an eddy current monitoring system, elements that may contribute an undesired signal to the sensed eddy current signal may be fabricated from a non-conductive material such as plastic or ceramic. In some implementations, elements may be fabricated from non-magnetic materials.

1 . A carrier head, comprising: 
 a substrate backing assembly having non-conductive rigid components, the substrate backing assembly to provide a mounting surface for a substrate to be polished.    
     
     
         2 . The carrier head of  claim 1 , further comprising a base assembly coupled with the substrate backing assembly, wherein components of the base assembly with at least a portion positioned within a sensing distance of the mounting surface are nonconductive.  
     
     
         3 . The carrier head of  claim 2 , wherein the sensing distance is between about one tenth of an inch and about two inches.  
     
     
         4 . The carrier head of  claim 2 , wherein the base assembly includes a non-conductive gimbal mechanism to permit the base assembly to move with respect to a housing.  
     
     
         5 . The carrier head of  claim 1 , further including a non-conductive retaining ring secured to the base assembly with one or more non-magnetic fasteners.  
     
     
         6 . The carrier head of  claim 5 , wherein the non-magnetic fasteners are also non-conductive.  
     
     
         7 . The carrier head of  claim 1 , wherein the non-conductive rigid components are also non-magnetic.  
     
     
         8 . The carrier head of  claim 1 , wherein the substrate backing assembly includes a non-conductive plate proximate to an upper surface of a flexible membrane.  
     
     
         9 . The carrier head of  claim 8 , wherein the non-conductive plate is selected from the group consisting of a plastic plate and a ceramic plate.  
     
     
         10 . The carrier head of  claim 1 , wherein the substrate backing assembly includes a flexible membrane and one or more clamp rings.  
     
     
         11 . The carrier head of  claim 1 , further comprising a housing coupled with the substrate backing assembly via a base assembly, wherein components of the housing with at least a portion positioned within a sensing distance of the mounting surface are nonconductive.  
     
     
         12 . The carrier head of  claim 11 , wherein the sensing distance is about one tenth of an inch.  
     
     
         13 . The carrier head of  claim 11 , wherein the sensing distance is between about one tenth of an inch and about two inches.  
     
     
         14 . A carrier head comprising: 
 a housing to be secured to a drive shaft, the housing including one or more housing elements;    a base assembly, the base assembly including one or more base elements, the one or more base elements including means for permitting the base assembly to move with respect to the housing; and    a flexible membrane secured to the base assembly, the flexible membrane having a lower surface that provides a substrate-mounting surface, and wherein the base elements having at least a portion within a minimum distance of the lower surface are non-conductive, and further wherein the housing elements having at least a portion within the minimum distance are non-conductive.    
     
     
         15 . The carrier head of  claim 14 , wherein the minimum distance is about one tenth of an inch.  
     
     
         16 . The carrier head of  claim 14 , wherein the minimum distance is between about one tenth of an inch and about two inches.