Polishing apparatus

Abstract

A polishing apparatus ( 1 ) has a polishing pad ( 22 ), a top ring ( 20 ) for holding a semiconductor wafer (W), a vertical movement mechanism ( 24 ) operable to move the top ring ( 20 ) in a vertical direction, a distance measuring sensor ( 46 ) operable to detect a position of the top ring ( 20 ) when a lower surface of the top ring ( 20 ) is brought into contact with the polishing pad ( 22 ), and a controller ( 47 ) operable to calculate an optimal position of the top ring ( 20 ) to polish the semiconductor wafer (W) based on the position detected by the distance measuring sensor ( 46 ). The vertical movement mechanism ( 24 ) includes a ball screw mechanism ( 30, 32, 38, 42 ) operable to move the top ring ( 20 ) to the optimal position.

1 . A top ring for holding a substrate and pressing the substrate against a polishing surface of a polishing pad on a polishing table, said top ring comprising;
 a top ring body configured to press the substrate against the polishing surface; and   a retainer ring configured to press the polishing surface, said retainer ring being provided at a peripheral portion of said top ring body,   said retainer ring comprising
 an elastic membrane shaped so as to form a pressure chamber therein, said elastic membrane being expandable and contractible vertically while pressing the substrate against the polishing surface, 
 a holder for securing said elastic membrane to said top ring body, said holder having a passage through which said pressure chamber communicates with a fluid supply source, and 
 a ring member to be pressed against the polishing surface by said pressure chamber supplied with a pressurized fluid therein, said ring member being vertically movable independently of said top ring body. 
   
     
     
         2 . The top ring according to  claim 1 , wherein said elastic membrane has bent portions. 
     
     
         3 . The top ring according to  claim 2 , wherein said elastic membrane comprises a rolling diaphragm. 
     
     
         4 . The top ring according to  claim 1 , wherein said elastic membrane is shaped so as to widen said pressure chamber when an inner pressure in said pressure chamber is increased. 
     
     
         5 . The top ring according to  claim 1 , further comprising an elastic membrane attached to a lower surface of said top ring body and shaped so as to contact substantially an entire upper surface of the substrate. 
     
     
         6 . The top ring according to  claim 5 , wherein a central chamber, a ripple chamber, an outer chamber, and an edge chamber are formed by said elastic membrane attached to the lower surface of said top ring body. 
     
     
         7 . The top ring according to  claim 1 , further comprising a retainer ring wear detector configured to measure an amount of wear of said retainer ring. 
     
     
         8 . An apparatus for polishing a substrate, comprising:
 a polishing table for supporting a polishing pad thereon; and   a top ring according to  claim 1 .   
     
     
         9 . A method of polishing a substrate by providing a sliding contact between the substrate and a polishing surface of a polishing pad on a polishing table, said method comprising;
 rotating the polishing table together with the polishing pad;   pressing the substrate against the polishing surface by a top ring while pressing a retainer ring against the polishing surface by a pressure chamber formed by an elastic membrane, said elastic membrane being expandable and contractible vertically while pressing the substrate against the polishing surface;   during said pressing of the substrate, rotating the top ring together with the substrate; and   adjusting a pressing force of the retainer ring against the polishing surface by adjusting pressure of a pressurized fluid to be supplied to the pressure chamber,   
     
     
         10 . The method according to  claim 9 , wherein said elastic membrane has bent portions. 
     
     
         11 . The method according to  claim 9 , wherein said pressing of the substrate against the polishing surface comprises pressing the substrate against the polishing surface via a central chamber, a ripple chamber, an outer chamber, and an edge chamber. 
     
     
         12 . A polishing apparatus comprising:
 a polishing surface; and   a top ring for holding a substrate, said top ring having a retainer ring for holding a peripheral portion of the substrate,   wherein said retainer ring includes
 an elastic membrane having a pressure chamber formed therein, said elastic membrane being expandable and contractible vertically, 
 a passage for supplying a fluid to the pressure chamber to vertically expand or contract said elastic membrane, and 
 a ring member vertically movable according to a vertical movement of said elastic membrane, said ring member being brought into contact with said polishing surface. 
   
     
     
         13 . The polishing apparatus according to  claim 12 , wherein said retainer ring further includes
 a cylinder housing said elastic membrane therein,   a holder configured to hold said elastic membrane on said cylinder, and   a piston vertically movable within said cylinder, said piston being connected to said elastic membrane.