Method and apparatus for polishing a wafer with a higher in-plane uniformity

Abstract

A wear thickness for a retainer ring is measured at a specified timing. The height of the retainer ring or the polishing condition of the polishing apparatus is changed in an amount greater than or equal to the wear thickness of the retainer ring. This compensates for the wear thickness of the retainer ring which degrades the within wafer uniformity of polishing rate due to a change in the bottom surface of the retainer ring.

1 . A method for polishing an object wafer by using a polishing apparatus including a retainer ring for guiding the object wafer in an in-plane direction of the object wafer, a pressure member for pressing a bottom surface of the object wafer in a thickness direction of the object wafer, and a polishing pad for polishing a top surface of the object wafer, said method comprising the steps of:
 obtaining a wear thickness of the retainer ring at a specific timing during or after polishing the object wafer in a first polishing condition;   calculating a correction amount of a polishing condition based on said obtained wear thickness; and   polishing the object wafer in a second polishing condition obtained by adding said calculated correction amount to said first polishing condition.   
     
     
         2 . The method according to  claim 1 , wherein said correction amount includes a first correction amount corresponding to said obtained wear thickness and a second correction amount corresponding to shape change of the retainer ring. 
     
     
         3 . The method according to  claim 1 , wherein said first polishing condition includes a first height of the retainer ring, said calculating step calculates a height correction amount corresponding to said obtained wear thickness, and said polishing step uses a second height of the retainer ring obtained by adding said height correction amount to said first height of the retainer ring. 
     
     
         4 . The method according to  claim 3 , wherein said height correction amount corresponds to a change in a thickness of said obtained wear thickness. 
     
     
         5 . The method according to  claim 1 , wherein said calculating step calculates said correction amount by using an approximation formula. 
     
     
         6 . The method according to  claim 1 , wherein said wear thickness obtaining step measures a depth of a groove formed on a surface of the retainer ring in contact with said polishing pad. 
     
     
         7 . The method according to  claim 1 , wherein said wear thickness obtaining step estimates said wear thickness based on a cumulative time length for polishing by the retainer ring and a polishing condition used in the polishing for the cumulative time length. 
     
     
         8 . A method for polishing an object wafer by using a polishing apparatus including a retainer ring for guiding the object wafer in an in-plane direction of the object wafer, a pressure member for pressing a bottom surface of the object wafer in a thickness direction of the object wafer, and a polishing pad for polishing a top surface of the object wafer, said method comprising the steps of:
 obtaining a wear thickness of the retainer ring at a specific timing during or after polishing the object wafer by using the retainer ring located at a first height;   calculating a correction amount of a height of the retainer ring based on said obtained wear amount, the calculated correction amount being larger than a correction amount corresponding to said obtained wear thickness; and   polishing the object wafer by using the retainer ring located at a second height obtained by adding said calculated correction amount to said first height.   
     
     
         9 . The method according to  claim 8 , wherein said calculating step calculates said correction amount by using an approximation formula. 
     
     
         10 . The method according to  claim 8 , wherein said wear thickness obtaining step measures a depth of a groove formed on a surface of the retainer ring in contact with said polishing pad. 
     
     
         11 . The method according to  claim 8 , wherein said wear thickness obtaining step estimates said wear thickness based on a time length for polishing the wafer and a polishing condition used at least in said first polishing condition. 
     
     
         12 . A polishing apparatus comprising:
 a retainer ring for guiding an object wafer in an in-plane direction of the object wafer;   a pressure member for pressing a bottom surface of the object wafer in a thickness direction of the object wafer;   a polishing pad for polishing a top surface of the object wafer:   a wear thickness determination unit for determining a wear thickness of the retainer ring at a specific timing during or after polishing the object wafer in a first polishing condition;   a calculation unit for calculating a correction amount of the polishing condition based on said determined wear thickness; and   a polishing unit for polishing the object wafer in a second polishing condition obtained by adding said calculated correction amount to said first polishing condition.   
     
     
         13 . The polishing apparatus according to  claim 12 , wherein said first polishing condition includes a first height of the retainer ring, said calculation unit calculates a height correction amount based on said obtained wear thickness, and said polishing controller polishes the object wafer by using a second height of the retainer ring obtained by adding said height correction amount to said first height of the retainer ring. 
     
     
         14 . The polishing apparatus according to  claim 13 , wherein said height correction amount includes a first correction amount corresponding to said obtained wear thickness and a second correction amount corresponding to shape change of the retainer ring. 
     
     
         15 . A polishing apparatus comprising:
 a retainer ring for guiding an object wafer in an in-plane direction of the object wafer,   a pressure member for pressing a bottom surface of the object wafer in a thickness direction of the object wafer,   a polishing pad for polishing a top surface of the object wafer;   a wear thickness determination unit for determining a wear thickness of the retainer ring at a specific timing after or during polishing the object wafer in a first polishing condition;   a calculation unit for calculating a correction amount of the retainer ring, which is larger than a correction amount corresponding to said determined wear thickness; and   a polishing unit for polishing the object wafer in a second polishing condition obtained by adding said calculated correction amount to said first polishing condition.