Composite polishing pad

Abstract

A polishing pad having an optically clear bottom layer and a closed cell top layer where the interface between the top and bottom layers is only a urethane to urethane interface. Grooves may be machined into the top layer or through the top layer and into the bottom layer.

1 . A polishing pad comprising: 
 an optically clear bottom layer;    a closed cell polyurethane top layer; and    a plurality of grooves contained in the top layer.    
     
     
         2 . The polishing pad of  claim 1  wherein the plurality of grooves traverse the top layer and are present in at least a portion of the bottom layer.  
     
     
         3 . The polishing pad of  claim 1  wherein the optically clear bottom layer comprises a polyurethane.  
     
     
         4 . The polishing pad of  claim 1  wherein the top layer has a Shore D hardness that is greater than the bottom layer.  
     
     
         5 . The polishing pad of  claim 1  wherein the top layer has a Shore D hardness of 60.  
     
     
         6 . The polishing pad of  claim 1  wherein the bottom layer has a Shore D hardness within a range of 20 to 50.  
     
     
         7 . The polishing pad of  claim 1  wherein an interface between the top and bottom layers comprises a urethane to urethane bond.  
     
     
         8 . A method for making a polishing pad comprising the steps of: 
 providing a solid urethane piece having a cavity contained therein wherein said solid urethane piece comprises a first Shore D hardness;    pouring a liquid urethane formulation into the cavity of the solid urethane piece wherein the liquid urethane formulation comprises a hardness formulation having a second Shore D hardness;    allowing the liquid urethane formulation to solidify and cure;    machining the solid urethane piece to a desired thickness; and    machining the solidified liquid urethane formulation to a desired thickness.    
     
     
         9 . The method of  claim 8  further comprising the step of machining grooves into at least one of the solid urethane piece and the solidified liquid urethane formulation.  
     
     
         10 . The method of  claim 9  wherein the step of machining grooves comprises the step of machining grooves into both the solid urethane piece and the solidified liquid urethane formulation.  
     
     
         11 . The method of  claim 8  wherein values of the first Shore D hardness and the second Shore D hardness are distinct from one another.