Polishing pad with endpoint window

Abstract

A polishing pad for chemical mechanical polishing comprising a polishing layer having a top polishing surface, a bottom surface and a thickness. The polishing layer comprises a porous polishing material and a window region. An exposed top surface of the transparent window is recessed from the top polishing surface. The transparent window extends from the recess region to the bottom surface of the polishing pad. The transparent window is non-porous and a portion of the top surface of the peripheral portion adjacent to the transparent window is coplanar with the top surface of the transparent window and the exposed bottom surface of the transparent window is coplanar with the bottom surface of the polishing layer.

What is claimed is: 
     
         1 . A polishing pad for chemical mechanical polishing comprising a polishing layer having a top polishing surface, a bottom surface and a thickness, the polishing layer comprises a porous polishing material and a window region, wherein the window region comprises a transparent window that has an exposed top surface and an exposed bottom surface to enable light to transmit through the polishing pad in the window region, the exposed top surface of the transparent window is recessed from the top polishing surface, the transparent window extending from the recess region to the bottom surface of the polishing pad, the window region further comprises a peripheral portion of the polishing material in contact with side edges of the transparent window, the peripheral portion of polishing material has a top surface that is recessed from the top surface of the top polishing surface and wherein the transparent window is non-porous and wherein a portion of the top surface of the peripheral portion adjacent to the transparent window is coplanar with the top surface of the transparent window and wherein the exposed bottom surface of the transparent window is coplanar with the bottom surface of the polishing layer. 
     
     
         2 . The polishing pad of  claim 1  wherein there are no chemical bonds between the transparent window and the polishing layer. 
     
     
         3 . The polishing pad of  claim 1  wherein the top polishing surface comprises grooves. 
     
     
         4 . The polishing pad of  claim 3  wherein the grooves intersect with in the peripheral portion of the window region. 
     
     
         5 . The polishing pad of  claim 1  further comprising a sub-pad adjacent to the polishing layer and opposite from the top polishing surface wherein the sub-pad includes an opening in the window region to enable light to transmit through the transparent window. 
     
     
         6 . The polishing pad of  claim 1  wherein the peripheral portion has a width greater than or equal to a thickness of the transparent window. 
     
     
         7 . The polishing pad of  claim 1  wherein the peripheral portion has a width greater than a thickness of the transparent window. 
     
     
         8 . A method of forming the polishing pad of  claim 1  comprising placing a plug of transparent window material in a mold and forming the polishing layer around the plug,
 cutting away a portion of the polishing layer to form the window region including the recessed window and the recessed peripheral portion of the polishing material. 
 
     
     
         9 . The method of  claim 7  wherein the forming comprises forming a thick slab that is cut into multiple polishing layers each having transparent window material extending through the thickness and the cutting away includes removal of a top portion of the transparent window material. 
     
     
         10 . A method of polishing comprising
 providing a substrate to be polished   providing the polishing pad as in  claim 1     providing a semi-transparent slurry on the polishing pad,   moving the substrate relative to the polishing pad,   transmitting light through the transparent window material and detecting light reflected from the substrate back through the transparent window and semi-transparent slurry to determine when polishing is complete.