Polishing apparatus

Abstract

A polishing apparatus for polishing a substrate is provided. The polishing apparatus includes: a polishing table holding a polishing pad; a top ring configured to press the substrate against the polishing pad; first and second optical heads each configured to apply the light to the substrate and to receive reflected light from the substrate; spectroscopes each configured to measure at each wavelength an intensity of the reflected light received; and a processor configured to produce a spectrum indicating a relationship between intensity and wavelength of the reflected light. The first optical head is arranged so as to face a center of the substrate, and the second optical head is arranged so as to face a peripheral portion of the substrate.

What is claimed: 
     
         1 . A polishing pad for a substrate polishing apparatus, the polishing pad being held on a polishing table that is configured to rotate around its own axis, the polishing pad comprising:
 a first surface that is in contact with the polishing table;   a second surface that is opposite to the first surface and is pressed against a substrate held by a top ring so as to polish the substrate;   a first through-hole extending from the first surface to the second surface, the first through-hole being configured to allow the light to pass therethrough from a first optical head disposed in the polishing table, the first through-hole being arranged to move in a first path that extends across the center of the top ring while the polishing pad on the polishing table makes one revolution, the first path extending from one side to an opposite side of the top ring in substantially a diametrical direction; and   a second through-hole extending from the first surface to the second surface, the second thorough-hole being configured to allow the light to pass therethrough from a second optical head disposed in the polishing table, the second through-hole being arranged to move in a second path that extends across only an annular region of the top ring when the first through-hole is not present under the top ring while the polishing pad with the polishing table makes one revolution.   
     
     
         2 . The polishing pad according to  claim 1 , wherein an angle between a line interconnecting the first through-hole and the center of the polishing pad and a line interconnecting the second through-hole and the center of the polishing pad is larger than 0 degrees. 
     
     
         3 . The polishing pad according to  claim 1 , wherein the first through-hole and the second through-hole are located at opposite sides with respect to the center of the polishing pad. 
     
     
         4 . The polishing pad according to  claim 1 , wherein a distance from the center of the polishing pad to the first through-hole is different from a distance from the center of the polishing pad and the second through-hole. 
     
     
         5 . The polishing pad according to  claim 1 , wherein the two through-holes are provided with transparent windows, respectively. 
     
     
         6 . A polishing pad for a substrate polishing apparatus, the polishing pad being held on a polishing table that is configured to rotate around its own axis and includes a retainer ring that can surround a substrate, the polishing pad comprising:
 a first surface that is in contact with the polishing table;   a second surface that is opposite to the first surface and is pressed against a substrate held by a top ring so as to polish the substrate;   a first through-hole extending from the first surface to the second surface, the first through-hole being configured to allow the light to pass therethrough from a first optical head disposed in the polishing table, the first through-hole being arranged to move in a first path that extends across the center of the top ring while the polishing pad on the polishing table makes one revolution, the first path extending from one side to an opposite side of the retainer ring in substantially a diametrical direction; and   a second through-hole extending from the first surface to the second surface, the second thorough-hole being configured to allow the light to pass therethrough from a second optical head disposed in the polishing table, the second through-hole being arranged to move in a second path that extends across only an annular region of the top ring when the first through-hole is not present under the top ring while the polishing pad with the polishing table makes one revolution.   
     
     
         7 . The polishing pad according to  claim 6 , wherein an angle between a line interconnecting the first through-hole and the center of the polishing pad and a line interconnecting the second through-hole and the center of the polishing pad is larger than 0 degrees. 
     
     
         8 . The polishing pad according to  claim 6 , wherein the first through-hole and the second through-hole are located at opposite sides with respect to the center of the polishing pad. 
     
     
         9 . The polishing pad according to  claim 6 , wherein a distance from the center of the polishing pad to the first through-hole is different from a distance from the center of the polishing pad and the second through-hole. 
     
     
         10 . The polishing pad according to  claim 6 , wherein the two through-holes are provided with transparent windows, respectively. 
     
     
         11 . A polishing pad for a substrate polishing apparatus, the polishing pad being held on a polishing table that is configured to rotate around its own axis and includes a membrane defining a circular pressure chamber and a plurality of annular pressure chambers, the polishing pad comprising:
 a first surface that is in contact with the polishing table;   a second surface that is opposite to the first surface and is pressed against a substrate held by a top ring so as to polish the substrate;   a first through-hole extending from the first surface to the second surface, the first through-hole being configured to allow the light to pass therethrough from a first optical head disposed in the polishing table, the first through-hole being arranged to move in a first path that extends across the center of the top ring while the polishing pad on the polishing table makes one revolution, the first path extending from one side to an opposite side of an outermost one of the plurality of annular pressure chambers in substantially a diametrical direction; and   a second through-hole extending from the first surface to the second surface, the second thorough-hole being configured to allow the light to pass therethrough from a second optical head disposed in the polishing table, the second through-hole being arranged to move in a second path that extends across only at least one annular pressure chamber, corresponding to a peripheral portion of the substrate, of the plurality of annular pressure chambers when the first through-hole is not present under the top ring while the polishing pad with the polishing table makes one revolution.   
     
     
         12 . The polishing pad according to  claim 11 , wherein an angle between a line interconnecting the first through-hole and the center of the polishing pad and a line interconnecting the second through-hole and the center of the polishing pad is larger than 0 degrees. 
     
     
         13 . The polishing pad according to  claim 11 , wherein the first through-hole and the second through-hole are located at opposite sides with respect to the center of the polishing pad. 
     
     
         14 . The polishing pad according to  claim 11 , wherein a distance from the center of the polishing pad to the first through-hole is different from a distance from the center of the polishing pad and the second through-hole. 
     
     
         15 . The polishing pad according to  claim 11 , wherein the two through-holes are provided with transparent windows, respectively.