Polishing pad with endpoint window

Abstract

A polishing pad for chemical mechanical polishing comprising a porous polishing layer having a top polishing surface, a sub-pad located opposite from the top polishing surface, the sub-pad having a bottom sub-pad surface, and a window for transmitting a signal wave through the polishing pad to a substrate to be polished and back through the polishing pad for endpoint detection, the window having a top window surface, a bottom window surface, and side edges, wherein the top window surface is recessed from the top polishing surface, the bottom window surface is substantially coplanar with the bottom sub-pad surface, the window extending from the bottom sub-pad surface to the top window surface and the side edges are in contact with the polishing material and the sub-pad material and wherein the window is non-porous.

What is claimed is: 
     
         1 . A polishing pad for chemical mechanical polishing comprising
 a porous polishing layer having a top polishing surface,   a sub-pad located opposite from the top polishing surface, the sub-pad having a bottom sub-pad surface, and   a window for transmitting a signal wave through the polishing pad to a substrate to be polished and back through the polishing pad for endpoint detection, the window having a top window surface, a bottom window surface, and side edges, wherein the top window surface is recessed from the top polishing surface, the bottom window surface is substantially coplanar with the bottom sub-pad surface, the window extending from the bottom sub-pad surface to the top window surface and the side edges are in contact with the polishing material and the sub-pad material and wherein the window is non-porous.   
     
     
         2 . The polishing pad of  claim 1  wherein the window comprises, a top window portion defining the top window surface; and an encapsulating layer portion defining the bottom window surface. 
     
     
         3 . The polishing pad of  claim 1  further comprising an encapsulating layer in contact with the bottom window surface and the bottom sub-pad surface. 
     
     
         4 . The polishing pad of  claim 1  wherein a portion of the polishing layer in contact with the side edges of the window forms a peripheral region that is recessed from the top polishing surface. 
     
     
         5 . The polishing pad of  claim 4  wherein a top surface of the peripheral portion adjacent to the window is coplanar with the top surface of the window. 
     
     
         6 . The polishing pad of  claim 1  wherein the top polishing surface comprises grooves. 
     
     
         7 . The polishing pad of  claim 1  wherein the top surface of the window is recessed below the polishing surface to a depth of 0.1 to 1.1 mm. 
     
     
         8 . The polishing pad of  claim 4  wherein the recessed peripheral portion of polishing layer ha a top surface that is recessed 0.1 to 1.1 mm from the top surface of the top polishing surface and the top recessed surface has a width of 0.1 to 1.1 mm. 
     
     
         9 . The polishing pad of  claim 1  wherein there are no chemical bonds between the window and the polishing layer. 
     
     
         10 . A method of polishing comprising
 providing a substrate to be polished   providing the polishing pad as in  claim 1     providing a slurry on the polishing pad,   moving the substrate relative to the polishing pad,   transmitting a signal wave through the window material and slurry and detecting the signal wave reflected from the substrate back through the window and slurry to determine when polishing is complete.