Polishing pad with endpoint detection window

Abstract

A polishing pad for chemical mechanical polishing of a substrate (e.g., a semiconductor wafer) comprises a polishing layer, a subpad layer, a top window portion, bottom window portion, and a support. The support extends from the polishing layer toward and is adjacent to a top window peripheral surface. The bottom window portion has a larger cross-section than the top window portion. The pad includes a gap between the bottom window peripheral surface and the subpad material. The pad can be used for endpoint using optical detection, acoustic detection, or both.

What is claimed is: 
     
         1 . A polishing pad  1  for chemical mechanical polishing comprising:
 a polishing layer  10  having a polishing surface  11  and a polishing layer interface surface  13  opposite the polishing surface  11 , the polishing layer  10  comprising a polishing material  14 , 
 a subpad layer  20  having a subpad interface surface  23  adjacent to the polishing layer interface surface  13  and a bottom surface  21  opposite the subpad interface surface, the subpad layer comprising a subpad material  24 , 
 a top window portion  30  comprising a top window material  34 , the top window material  34  having a polishing face surface  31  recessed from the polishing surface  11 , a top window interface surface  33  opposite the polishing face surface, and a top window peripheral surface  32  extending from the polishing face surface  31  to the top window interface surface  33 , 
 a support  60  extending from the polishing layer  10  toward and adjacent to the top window peripheral surface  32 , the support  60  including a top support surface  61  and a support interface surface  63  opposite from the top support surface  61 , 
 a bottom window portion  40 , having a bottom window interface surface  43 , a bottom window bottom surface  41  and a bottom window peripheral surface  42  that extends from the bottom window interface surface to the bottom window bottom surface, wherein a region defined by the bottom window bottom surface  41 , the bottom window peripheral surface  42  and the bottom window interface surface  43  is filled with a bottom window material  44 , 
 wherein the bottom window interface surface  43  is adjacent the top window interface surface  33  and adjacent to at least a portion of the support interface surface  63 , 
 wherein there is a gap  45  between the bottom window peripheral surface  42  and the subpad material. 
 
     
     
         2 . The polishing pad of  claim 1  wherein a top of the gap  45  is defined by the support interface surface  63 . 
     
     
         3 . The polishing pad of  claim 1  wherein a top of the gap  45  is defined by the support interface surface  63  and by the polishing interface surface  13 . 
     
     
         4 . The polishing pad of  claim 1  wherein the top support surface is coplanar with the polishing face surface of the top window portion. 
     
     
         5 . The polishing pad of  claim 1  wherein the bottom window material is elastomeric. 
     
     
         6 . The polishing pad of  claim 1  wherein the support interface surface is coplanar with the polishing layer interface surface, with the top window interface surface, or both. 
     
     
         7 . The polishing pad of  claim 1  wherein a seal is formed between the support and the top window material. 
     
     
         8 . The polishing layer of  claim 1  wherein the support is integral with the polishing layer. 
     
     
         9 . The polishing layer of  claim 1  wherein the top window material and the bottom window material are transmissive of radiation used for optical signals such that the polishing pad are suitable for both optical end point detection and vibrational end point detection. 
     
     
         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 detecting the signal wave reflected from the substrate back through the window and slurry to determine when polishing is complete.