Multifunctional endpoint detection window

Abstract

A polishing pad having a window extending through the polishing pad from the polishing surface to a backside surface of the pad. The window includes a top window material separated from a polishing material, a bottom window wherein the bottom window material is elastomeric and can deform into a void space adjacent to the bottom window material when the pad is under pressure during polishing. A seal between the subpad material and the top window material and/or bottom window material or a seal between the polishing layer and the bottom window material prevents particles or liquid used in the chemical mechanical polishing from passing from above the polishing layer to below the subpad layer. The pad can be used for polishing with either optical or vibrational end-point detection.

What is claimed is: 
     
         1 . A polishing pad for chemical mechanical polishing comprising:
 a polishing layer having a polishing surface, a polishing layer interface surface opposite the polishing surface, and a polishing window region surface extending from the polishing surface to the polishing interface surface, the polishing layer comprising a polishing material,   a subpad layer having a subpad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite the subpad interface surface, and a bottom window regions interface surface extending from the bottom surface to the polishing layer interface surface, the subpad layer comprising a subpad material,   a window extending through the polishing pad from the polishing surface to a backside surface of the pad, the window comprising:
 a top window material having a polishing face surface, a top window peripheral surface, and a top window interface surface, the top window peripheral surface being adjacent to the top window regions surface and separated from the top window region surface such that the top window peripheral surface does not have direct contact with the window region surface, 
   and a bottom window material having a bottom window interface surface bonded to the top window interface surface a bottom window peripheral surface, a bottom window bottom surface wherein the bottom window material is elastomeric and can deform into a void space adjacent to the bottom window material when the pad is under pressure during polishing,   wherein a seal is formed (a) between subpad material and the top window material, the bottom window material, or a combination of the top window material and the bottom window material form a seal with the subpad material or (b) between the bottom window material and the polishing material to prevent particles or liquid used in the chemical mechanical polishing from passing from above the polishing layer to below the subpad layer, and   wherein the pad includes a path in the window region for transmitting columnated or non-columnated light through the thickness of the pad and wherein vibrational signals can be transmitted through the top window material and the bottom window material enabling acoustic end-point detection.   
     
     
         2 . The polishing pad of  claim 1  wherein the top window polishing face surface is recessed below the polishing surface. 
     
     
         3 . The polishing pad of  claim 1  having a void located inward from the bottom window peripheral surface that extends from the bottom window interface surface to the bottom window bottom surface. 
     
     
         4 . The polishing pad of  claim 1  having a void located between the bottom window peripheral surface and the subpad layer window region surface. 
     
     
         5 . The polishing pad of  claim 4  having a void located between the bottom window peripheral surface and the subpad layer window region surface. 
     
     
         6 . The polishing pad of  claim 1  including an encapsulating layer adjacent to the bottom window bottom surface. 
     
     
         7 . The polishing pad of  claim 6  wherein the encapsulating material extends across a void located between the bottom window peripheral surface and the subpad layer window region surface, across a void located inward from the bottom window peripheral surface that extends from the bottom window interface surface to the bottom window bottom surface  41 , or both, wherein the encapsulating material is transparent. 
     
     
         8 . The polishing pad of  claim 1  having an adhesive between the top window material and the bottom window material. 
     
     
         9 . The polishing pad of  claim 1  wherein the top window interface surface is in direct contact with the bottom window interface surface. 
     
     
         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;   polishing by moving the substrate relative to the polishing pad; and   monitoring polishing by (a) transmitting a light wave through the top window material and the void and detecting the light wave reflected from the substrate, (b) transmitting a vibrational signal through the top window material, the polishing layer material or both and through the bottom window material, or both (a) and (b).