Apparatus for and method for polishing workpiece

Abstract

A polishing apparatus for polishing a workpiece such as a semiconductor wafer has a turntable with a polishing surface, and a top ring for holding a workpiece and pressing the workpiece against the polishing surface under a first pressing. The polishing apparatus has a pressurized fluid source for supplying pressurized fluid, and a plurality of openings provided in the holding surface of the top ring for ejecting the pressurized fluid supplied from the pressurized fluid source. A plurality of areas each having the openings are defined on the holding surface so that the pressurized fluid is selectively ejectable from the openings in the respective areas.

1. A polishing apparatus for polishing a surface of a workpiece comprising:
 a turntable having a polishing surface thereon;  
 a top ring for supporting the workpiece to be polished and pressing the workpiece against said polishing surface under a first pressing force, said top ring having a holding surface for holding the workpiece;  
 a pressurized fluid source for supplying pressurized fluid;  
 a plurality of openings provided in said holding surface of said top ring for ejecting said pressurized fluid supplied from said pressurized fluid source, a plurality of areas each having said openings being defined in said holding surface so that said pressurized fluid is selectively ejectable from said openings in said respective areas.  
 
     
     
       2. An apparatus according to  claim 1 , wherein said plurality of areas comprises concentric annular areas. 
     
     
       3. An apparatus according to  claim 1 , wherein said plurality of areas are defined by communicating with a plurality of chambers, respectively formed in said top ring through said openings. 
     
     
       4. An apparatus according to  claim 1 , wherein said first pressing force and a pressure of said pressurized fluid are variable independently of each other. 
     
     
       5. An apparatus according to  claim 1 , wherein a pressure of said pressurized fluid is variable in each of said areas. 
     
     
       6. An apparatus according to  claim 1 , further comprising:
 a presser ring vertically movably disposed around said top ring; and  
 a pressing device for pressing said presser ring against said polishing surface under a second pressing force which is variable.  
 
     
     
       7. An apparatus according to  claim 1 , wherein said top ring has a recess defined therein for accommodating the workpiece therein. 
     
     
       8. A method of polishing a workpiece, comprising the steps of:
 holding a workpiece between a polishing surface of a turntable and a holding surface of a top ring disposed above said turntable;  
 pressing the workpiece by said top ring against said polishing surface under a first pressing force; and  
 ejecting pressurized fluid from openings in a plurality of areas in said holding surface of said top ring toward the workpiece held by said top ring, said pressurized fluid being selectively ejectable from said openings in said respective areas; and  
 polishing the workpiece in such a state that a pressing force applied to the workpiece by said pressurized fluid is variable in a central portion and an outer circumferential portion of the workpiece, respectively.  
 
     
     
       9. A method according to  claim 8 , further comprising the step of:
 pressing a presser ring vertically movably disposed around said top ring against said polishing surface around the workpiece under a second pressing force which is determined based on said first pressing force.  
 
     
     
       10. A method according to  claim 8 , said second pressing force is determined on the basis of a pressure distribution on the workpiece caused by said pressurized fluid ejected from said openings in said respective areas. 
     
     
       11. A top ring for supporting the workpiece to be polished, for use in a polishing apparatus, comprising:
 a holding surface for holding the workpiece; and  
 a plurality of openings, provided in said holding surface, from which pressurized fluid is ejected, a plurality of areas each having said openings being defined in said holding surface so that said pressurized fluid is selectively ejectable from said openings in said respective areas.  
 
     
     
       12. A method of polishing a surface of a workpiece, comprising:
   holding a workpiece by a top ring; and        pressing the workpiece against a polishing surface of a turntable to polish a surface of the workpiece by applying independently adjustable polishing pressures to substantially concentric circular areas of the workpiece, respectively, said polishing pressures including a first polishing pressure applied to a central circular area of the workpiece, a second polishing pressure applied to a first annular area of the workpiece located outside of the central circular area, and a third polishing pressure applied to a second annular area of the workpiece located outside of the first annular area.     
     
     
       13. A method according to  claim 12 , wherein said pressure is produced by air pressure. 
     
     
       14. A method according to  claim 12 , further comprising applying an adjustable pressure to a presser ring vertically movably disposed around said top ring for pressing said polishing surface. 
     
     
       15. A method according to  claim 14 , wherein said pressure applied to said presser ring is produced by air pressure. 
     
     
       16. A method according to  claim 12 , wherein the pressure applied to a central portion of the workpiece is larger than the pressure applied to an outer circumferential portion of the workpiece. 
     
     
       17. A method according to  claim 12 , wherein the pressure applied to an outer circumferential portion of the workpiece is larger than the pressure applied to a central portion of the workpiece. 
     
     
       18. A method of polishing a surface of a workpiece, the method comprising:
   holding a workpiece with a top ring;        applying a first polishing pressure to a central portion of the workpiece;        applying a second polishing pressure to an outer circumferential portion of the workpiece, wherein the first polishing pressure is different than the second polishing pressure, and the first and second polishing pressures are independently adjustable; and        pressing a presser ring against a polishing surface under a pressing force which is variable.     
     
     
       19. The method as claimed in  claim 18 , wherein the first and second polishing pressures are produced by air pressure. 
     
     
       20. The method as claimed in  claim 18 , wherein the first and second polishing pressures are produced by pressurized fluid. 
     
     
       21. The method as claimed in  claim 18 , wherein the polishing pressure applied to the central portion of the workpiece is larger than the polishing pressure applied to the outer circumferential portion of the workpiece. 
     
     
       22. The method as claimed in  claim 18 , wherein the polishing pressure applied to the outer circumferential portion of the workpiece is larger than the polishing pressure applied to the central portion of the workpiece. 
     
     
       23. The method as claimed in  claim 18 , wherein the polishing pressures can be independently changed at different locations of the workpiece. 
     
     
       24. The method as claimed in  claim 23 , wherein the number of different locations where the polishing pressures can be independently changed includes at least three different locations. 
     
     
       25. A method of polishing a surface of a workpiece comprising:
   holding a workpiece by a top ring;        pressing the workpiece by the top ring against a polishing surface;        supplying fluid pressures in a plurality of chambers formed in said top ring to provide polishing pressure to a central area and an outer circumferential area, wherein a radial width along a radius of said top ring of an outer one of said plurality of chambers is narrower than a radius of a central one of said plurality of chambers;        wherein said fluid pressures in said respective chambers are controllable independently of each other on the basis of the pressures detected by pressure sensors.     
     
     
       26. The method as claimed in  claim 25 , further comprising pressing a presser ring against the polishing surface. 
     
     
       27. The method as claimed in  claim 26 , wherein the pressing of the pressing ring is achieved by applying an adjustable pressure to the presser ring. 
     
     
       28. The method as claimed in  claim 24 , wherein the pressure applied to the presser ring is produced by air pressure. 
     
     
       29. A workpiece carrier for holding a workpiece and pressing the workpiece against a polishing surface, said workpiece carrier comprising:
   a top ring for supporting the workpiece to be polished;        a pressing mechanism for pressing the workpiece against the polishing surface, said pressing mechanism being configured to apply a first polishing pressure to a central circular area of the workpiece and a second polishing pressure to an annular area of the workpiece that is outside of the central circular area, wherein the first polishing pressure and the second polishing pressure are controllable independently of each other; and        a presser ring vertically movably disposed around said top ring, said presser ring being pressed against a polishing surface under a pressing force which is variable.     
     
     
       30. The workpiece carrier as claimed in  claim 29 , wherein said pressing mechanism comprises at least two pressurized chambers to which pressurized fluid is supplied, said at least two pressurized chambers comprising a central circular chamber and a first annular chamber located outside of said central circular chamber,
   said central circular chamber and said first annular chamber being positionable over the central circular area and the first annular area of the workpiece, respectively,        wherein said first polishing pressure and said second polishing pressure can be created by said pressurized fluid supplied to said central circular chamber and said first annular chamber, respectively.     
     
     
       31. The workpiece carrier as claimed in  claim 29 , wherein said first polishing pressure and said second polishing pressure are controllable independently of each other during polishing. 
     
     
       32. The workpiece carrier as claimed in  claim 29 , wherein said first polishing pressure and said second polishing pressure can be substantially uniformly applied to each of the central circular area and the first annular area of the workpiece. 
     
     
       33. The workpiece carrier as claimed in  claim 30 , wherein said first polishing pressure and said second polishing pressure are controllable by varying said pressurized fluid supplied to said central circular chamber and said first annular chamber, respectively. 
     
     
       34. The workpiece carrier as claimed in  claim 30 , wherein said pressurized fluid comprises pressurized air. 
     
     
       35. The workpiece carrier as claimed in  claim 30 , further comprising a second annular chamber located outside of said first annular chamber, wherein said second annular chamber can be positioned over a second annular area located outside of said first annular area of the workpiece so that a third polishing pressure, created by pressurized fluid supplied to said second annular chamber, can be applied to the second annular area of the workpiece. 
     
     
       36. The workpiece carrier as claimed in  claim 35 , wherein the pressurized fluid supplied to said second annular chamber comprises pressurized air. 
     
     
       37. A method for polishing a surface of a workpiece, the method comprising:
   holding a workpiece by a top ring;        pressing the workpiece against a polishing surface by applying polishing pressure to the workpiece, said polishing pressure including a first polishing pressure applied to a central circular area of the workpiece and a second polishing pressure applied to a first annular area of the workpiece located outside of said central circular area, said first polishing pressure and said second polishing pressure being controllable independently of each other; and        pressing a presser ring against said polishing surface under a pressing force which is variable.     
     
     
       38. The method as claimed in  claim 37 , further comprising applying a third polishing pressure to a second annular area of the workpiece located outside of the first annular area of the workpiece, the third polishing pressure being controllable independently of the first and second polishing pressures. 
     
     
       39. A method for polishing a surface of a workpiece, the method comprising:
   holding a workpiece by a top ring;        pressing the workpiece against a polishing surface by applying polishing pressure to the workpiece, the polishing pressure including a first polishing pressure applied to a central circular area of the workpiece and a second polishing pressure applied to a first annular area of the workpiece located outside of the central circular area of the workpiece,        the first polishing pressure and the second polishing pressure being controllable independently of each other; and        pressing an area of the polishing surface around the workpiece with a presser ring under a pressing force which is variable.     
     
     
       40. A method for polishing a surface of a workpiece, the method comprising:
   holding a workpiece by a top ring; and        pressing the workpiece against a polishing surface by applying polishing pressure to the workpiece, the polishing pressure including a first polishing pressure applied to a central circular area of the workpiece, a second polishing pressure applied to a first annular area of the workpiece located outside of the central circular area, and a third polishing pressure applied to a second annular area of the workpiece located outside of the first annular area; and        pressing a presser ring against said polishing surface under a pressing force which is variable.     
     
     
       41. A polishing apparatus for polishing a surface of a workpiece, comprising:
   a top ring for holding a workpiece, and        a plurality of chambers formed in said top ring, fluid pressures being supplied in said respective chambers to provide polishing pressure to a central area and an outer circumferential area, wherein a radial width along a radius of said top ring of an outer one of said plurality of chambers is narrower than a radius of a central one of said plurality of chambers.     
     
     
       42. A polishing apparatus according to  claim 41 , wherein said polishing pressure comprises a fluid pressure. 
     
     
       43. A polishing apparatus according to  claim 41 , wherein said polishing pressure comprises a compressed air pressure. 
     
     
       44. A polishing apparatus according to  claim 41 , wherein said central area and said outer circumferential area are formed by chambers formed in said top ring. 
     
     
       45. A polishing apparatus according to  claim 41 , further comprising:
   a third area located between said central area and said outer circumferential area.     
     
     
       46. A polishing apparatus according to  claim 41 , further comprising:
   a presser ring disposed around the workpiece and contacting a polishing surface for polishing the workpiece.     
     
     
       47. A polishing apparatus according to  claim 46 , wherein said presser ring is pressed by pressurized fluid. 
     
     
       48. A method for polishing a workpiece, comprising:
   holding a workpiece on a surface of a top ring; and        applying a polishing pressure on a surface of the workpiece, wherein an area where said polishing pressure is applied is divided into at least a central area and an outer circumferential area of the workpiece, and a radial width along a radius of said top ring of the outer circumferential area is narrower than a radius of the central area.     
     
     
       49. A method according to  claim 48 , wherein said polishing pressure comprises a fluid pressure. 
     
     
       50. A method according to  claim 48 , wherein said polishing pressure comprises a compressed air pressure. 
     
     
       51. A method according to  claim 48 , wherein said central area and said outer circumferential area are formed by chambers formed in said top ring. 
     
     
       52. A method according to  claim 48 , wherein the area where said polishing pressure is applied is divided to said central area, said outer circumferential area and a third area located between said central area and said outer circumferential area. 
     
     
       53. A method according to  claim 48 , further comprising:
   pressing a presser ring disposed around the workpiece against a polishing surface for polishing the workpiece.     
     
     
       54. A method according to  claim 53 , wherein said presser ring is pressed by pressurized fluid.