Retainer ring and method for polishing a workpiece

Abstract

A chemical mechanical polishing (CMP) machine ( 20 ) includes a workpiece carrier assembly ( 22 ) having a carrier base ( 24 ) with a workpiece contacting side ( 26 ) for holding a first surface ( 30 ) of a workpiece ( 32 ). A method utilizing the CMP machine ( 20 ) to polish the workpiece ( 32 ) and achieve a minimal edge exclusion region ( 92 ) entails adapting the carrier base ( 24 ) to reduce a first diameter ( 53 ) of a workpiece contacting side ( 26 ) of the carrier base ( 24 ) to a second diameter ( 84 ). The method further calls for providing a retainer ring ( 68, 106 ) disposed concentrically on the carrier base ( 24 ) for retaining the workpiece ( 32 ), and applying pressure on the carrier base ( 24 ) to urge a second surface ( 34 ) of the workpiece ( 36 ) against a polishing pad ( 36 ) of the CMP machine ( 20 ). In a first embodiment, the retainer ring ( 68 ) includes a body portion ( 70 ) and a holding lip ( 78 ) protruding radially inward from an inner periphery ( 80 ) of the body portion ( 70 ) and overlying an outer edge of the workpiece ( 32 ) to reduce the first diameter ( 53 ) of the workpiece contacting side ( 26 ) to the second diameter ( 84 ). In an alternative embodiment, the carrier base ( 24 ) is modified to reduce the first diameter ( 53 ) of the workpiece contacting side to the second diameter ( 84 ). Correspondingly, a width of the retainer ring 106 is defined to include a value substantially equivalent to one half of the difference between the first diameter ( 53 ) and the second diameter ( 84 ).

What is claimed is:  
     
         1 . A retainer ring for retaining a workpiece within a workpiece carrier assembly of a polishing machine, said workpiece carrier assembly including a carrier base for holding a first surface of said workpiece and for abutting a second surface, opposite said first surface, of said workpiece against a polishing pad of said polishing machine, said retainer ring comprising: 
 a body portion configured to be disposed concentrically on an outer periphery of said carrier base; and    a holding lip for retaining said workpiece, said holding lip protruding radially inward from an inner periphery of said body portion.    
     
     
         2 . A retainer ring as claimed in  claim 1  wherein said body portion is configured to be coupled to said carrier base.  
     
     
         3 . A retainer ring as claimed in  claim 1  wherein when said workpiece is held in said carrier base, said holding lip is configured to approach a perimeter of said workpiece to minimize a gap between said holding lip and said perimeter.  
     
     
         4 . A retainer ring as claimed in  claim 1  wherein said holding lip exhibits a width, said width protruding radially inward, and said width being in a range of 0.005 and 0.012 inches.  
     
     
         5 . A retainer ring as claimed in  claim 4  wherein said width of said holding lip is substantially 0.010 inches.  
     
     
         6 . A retainer ring as claimed in  claim 1  wherein said carrier base includes a workpiece contacting side having a first diameter, and said holding lip is configured to overlie an outer edge of said workpiece contacting side of said carrier base to reduce said first diameter of said workpiece contacting side to a second diameter.  
     
     
         7 . A retainer ring as claimed in  claim 1  wherein said holding lip exhibits a height configured to accommodate a thickness of said workpiece.  
     
     
         8 . A retainer ring as claimed in  claim 1  wherein said retainer ring is adapted to replace an existing retainer ring of said workpiece carrier assembly.  
     
     
         9 . A method for utilizing a polishing machine to polish a workpiece to achieve a minimal edge exclusion region, said polishing machine including a workpiece carrier assembly having a carrier base with a workpiece contacting side for holding a first surface of said workpiece, said workpiece contacting side exhibiting a first diameter, and said method comprising: 
 adapting said carrier base to reduce said first diameter of said workpiece contacting side to a second diameter;    providing a retainer ring disposed concentrically on an outer periphery of said carrier base for retaining said workpiece when said workpiece is held by said carrier base; and    applying pressure on an upper side, opposite from said workpiece contacting side, of said carrier base to urge a second surface of said workpiece into sliding engagement with a polishing pad of said polishing machine.    
     
     
         10 . A method as claimed in  claim 9  wherein said carrier base is an existing carrier base exhibiting said first diameter, and said adapting operation includes modifying said existing carrier base to reduce said first diameter of said workpiece contacting side to obtain said second diameter.  
     
     
         11 . A method as claimed in  claim 10  wherein said providing operation comprises defining a width of said retainer ring to include a value substantially equivalent to one half of a difference between said first diameter and said second diameter.  
     
     
         12 . A method as claimed in  claim 11  wherein said value is in a range of 0.005 to 0.012 inches.  
     
     
         13 . A method as claimed in  claim 9  wherein said carrier base is an existing carrier base exhibiting said first diameter, and said providing operation includes: 
 producing said retainer ring having a body portion and a holding lip protruding radially inward from an inner periphery of said body portion, said body portion being configured to be disposed concentrically on said outer periphery of said carrier base; and  
 positioning said retaining ring such that said holding lip overlies an outer edge of said workpiece contacting side of said carrier base to reduce said first diameter of said workpiece contacting side to obtain said second diameter.  
 
     
     
         14 . A method as claimed in  claim 13  wherein said producing operation includes establishing a width of said holding lip to be substantially equivalent to one half of a difference between said first diameter and said second diameter.  
     
     
         15 . A method as claimed in  claim 14  wherein said width of said holding lip is in a range of 0.005 to 0.012 inches.  
     
     
         16 . A workpiece carrier assembly retrofit kit for adapting a workpiece carrier assembly of a polishing machine to polish a workpiece having a minimal edge exclusion region, said workpiece carrier assembly including an existing carrier base and an existing retainer ring coupled to said existing carrier base, said existing carrier base having a workpiece contacting side exhibiting a first diameter, said existing retainer ring exhibiting a first width, and said kit comprising: 
 a carrier base configured to replace said existing carrier base, said carrier base having a workpiece contacting side exhibiting a second diameter, said second diameter being less than said first diameter of said existing carrier base; and    a retaining ring configured to couple to said carrier base, said retaining ring exhibiting a second width, said second width being substantially equivalent to a sum of said first width and a value substantially equivalent to one half of a difference between said first diameter and said second diameter.