Multiple window pad assembly

Abstract

A method and apparatus for detecting and obtaining a metric indicative of a polishing process is described. The apparatus includes a polishing pad having an optically transparent region adapted to obtain polishing metric from at least one substrate from at least two distinct radial positions of the polishing pad. The method includes obtaining a polishing metric from at least two substrates being polished simultaneously on a single polishing pad.

1 . A polishing pad assembly, comprising:
 a circular body comprising a polishing material having a polishing surface; and   at least two portions formed in the polishing surface that are transparent to light and electromagnetic radiation, each of the at least two portions comprising a transmissive window disposed below a plane defined by the polishing surface and the transmissive window is coupled to the body by a bonding agent.   
     
     
         2 . The polishing pad assembly of  claim 1 , wherein the at least two portions are disposed at different radial positions within the circular body. 
     
     
         3 . The polishing pad assembly of  claim 1 , wherein the circular body comprises a supporting layer. 
     
     
         4 . The polishing pad assembly of  claim 3 , wherein the transmissive window is adhered to the supporting layer. 
     
     
         5 . The polishing pad assembly of  claim 3 , wherein the supporting layer comprises a material that is transparent to light and electromagnetic radiation. 
     
     
         6 . The polishing pad assembly of  claim 3 , wherein the at least two portions are disposed in the supporting layer. 
     
     
         7 . The polishing pad assembly of  claim 1 , wherein the circular body comprises an adhesive layer opposite the polishing surface. 
     
     
         8 . The polishing pad assembly of  claim 7 , wherein the adhesive layer is transparent to light and electromagnetic radiation. 
     
     
         9 . A polishing pad assembly, comprising:
 a circular body comprising a polishing material having a polishing surface; and   a linear strip positioned along a portion of the radius of the polishing surface that is transparent to light and electromagnetic radiation, the linear strip occupying at least one half of the radius of the polishing surface and comprising a transmissive window coupled to the body by a bonding agent and disposed below a plane defined by the polishing surface.   
     
     
         10 . The polishing pad assembly of  claim 9 , wherein the circular body comprises a supporting layer. 
     
     
         11 . The polishing pad assembly of  claim 10 , wherein the transmissive window is adhered to the supporting layer. 
     
     
         12 . The polishing pad assembly of  claim 10 , wherein the supporting layer comprises a material that is transparent to light and electromagnetic radiation. 
     
     
         13 . The polishing pad assembly of  claim 9 , wherein the linear strip comprises one or more optical windows separated by a polishing material. 
     
     
         14 . The polishing pad assembly of  claim 9 , wherein the linear strip occupies about 75% of the radius of the polishing surface. 
     
     
         15 . The polishing pad assembly of  claim 9 , wherein the linear strip occupies about 90% of the radius of the polishing surface. 
     
     
         16 . A method for obtaining a polishing metric while polishing at least two substrates simultaneously on a single circular polishing pad, comprising:
 providing rotational movement of the polishing pad relative to each of the at least two substrates;   providing at least one optical sensor in selective communication with a surface of both of the at least two substrates at different radial positions;   emitting light or an electromagnetic signal toward each substrate at an interval corresponding with the rotational movement of the polishing pad; and   receiving a reflected signal from a surface of at least one of the substrates indicative of polishing progress.   
     
     
         17 . The method of  claim 16 , further comprising:
 moving the at least one optical sensor to different radial positions at each revolution of the polishing pad.   
     
     
         18 . The method of  claim 16 , further comprising:
 moving the at least one optical sensor to different radial positions at substantially each half revolution of the polishing pad.   
     
     
         19 . The method of  claim 16 , wherein the interval equals one revolution of the polishing pad. 
     
     
         20 . The method of  claim 16 , wherein the interval equals every other revolution of the polishing pad.