Polishing head for polishing semiconductor wafers

Abstract

A polishing head and method for chucking a semiconductor wafer onto the polishing head uses a base structure and an outer flexible membrane with at least a first annular chamber and a second annular chamber positioned between the base structure and the outer flexible membrane. The polishing head includes a central cavity positioned below the base structure and at least partly defined by the outer flexible membrane, which is used to hold the semiconductor wafer onto the outer flexible membrane.

1 . A polishing head for polishing a semiconductor wafer comprising: 
 a base structure;    an outer flexible membrane positioned below said base structure such that at least a first annular chamber and a second annular chamber are positioned between said base structure and said outer flexible membrane, said second annular chamber being positioned to surround said first annular chamber, a lower surface of said outer flexible membrane being used to contact said semiconductor wafer;    a central cavity positioned below said base structure and at least partly defined by said outer flexible membrane, said central cavity being open at said lower surface of said outer flexible membrane;    a first fluid channel connected to said first annular chamber to supply pressurized fluid and to apply suction to said first chamber;    a second fluid channel connected to said second annular chamber to supply pressurized fluid to said second chamber; and    a third fluid channel connected to said central cavity, said third fluid channel being used to apply suction directly to said semiconductor wafer through the central cavity to hold said semiconductor wafer onto said outer flexible membrane.    
     
     
         2 . The polishing head of  claim 1  further comprising: 
 a third annular chamber positioned between said base structure and said outer flexible membrane, said third annular chamber being positioned to surround said second annular chamber; and    a fourth fluid channel connected to said third annular chamber to supply pressurized fluid to said third chamber.    
     
     
         3 . The polishing head of  claim 1  wherein said outer flexible membrane includes an annular flap on an upper surface of said outer flexible membrane, said first annular chamber being at least partly defined by said annular flap and said upper surface of said outer flexible membrane and said base structure.  
     
     
         4 . The polishing head of  claim 3  wherein said outer flexible membrane includes another annular flap on said upper surface of said outer flexible membrane, said second annular chamber being at least partly defined by said annular flap, said another annular flap and said upper surface of said outer flexible membrane and said base structure.  
     
     
         5 . The polishing head of  claim 4  further comprising: 
 a third annular chamber positioned between said base structure and said outer flexible membrane, said third annular chamber being positioned to surround said second annular chamber, said third annular chamber being at least partly defined by said another annular flap and said upper surface of said outer flexible membrane and said base structure; and    a fourth fluid channel connected to said third annular chamber to supply pressurized fluid to said third chamber.    
     
     
         6 . The polishing head of  claim 3  further comprising an inner annular flexible membrane positioned between said base structure and said outer flexible membrane, said inner annular flexible membrane and said base structure at least partly defining said second annular chamber.  
     
     
         7 . The polishing head of  claim 6  further comprising a fourth fluid channel connected to a space between said outer flexible membrane and said inner annular flexible membrane, said fourth fluid channel being used to selectively apply suction to said space.  
     
     
         8 . The polishing head of  claim 6  further comprising: 
 another inner annular flexible membrane positioned between said base structure and said outer flexible membrane, said another inner annular flexible membrane being positioned to surround said inner annular flexible membrane, said another inner annular flexible membrane and said base structure at least partly defining a third annular chamber that surround said second annular chamber; and    a fourth fluid channel connected to said third annular chamber to supply pressurized fluid to said third chamber.    
     
     
         9 . The polishing head of  claim 1  wherein said base structure includes a base and a plurality of annular discs attached to a bottom surface of said base, said annular discs having bottom surfaces that at least partly define said first and second annular chambers.  
     
     
         10 . The polishing head of  claim 9  wherein said annular discs include a recess region on one of said bottom surfaces of said annular discs.  
     
     
         11 . The polishing head of  claim 9  wherein at least one of said annular discs has a vertical thickness that is less than the vertical thickness of other annular discs.  
     
     
         12 . The polishing head of  claim 1  wherein said outer flexible membrane is configured to include an annular upside down U-shaped portion.  
     
     
         13 . The polishing head of  claim 1  further comprising a housing attached to said base structure and a valve-and-regulator assembly positioned within said housing, said valve-and-regulator assembly being connected to said first and second fluid channels.  
     
     
         14 . The polishing head of  claim 13  wherein said valve-and-regulator assembly is configured to selectively provide suction to at least one of said first and second fluid channels to apply said suction to at least one of said first and second annular chambers.  
     
     
         15 . The polishing head of  claim 13  wherein said valve-and-regulator assembly is configured to selectively provide suction to said first fluid channel to apply said suction to said first annular chamber, and said valve-and-regulator assembly being further configured to selectively release fluid in said second annular chamber.  
     
     
         16 . A polishing head for polishing a semiconductor wafer comprising: 
 a base structure;    an outer flexible membrane positioned below said base structure such that at least a first annular chamber and a second annular chamber are positioned between said base structure and said outer flexible membrane, said second annular chamber being positioned to surround said first annular chamber, a lower surface of said outer flexible membrane being used to contact said semiconductor wafer;    a central cavity positioned below said base structure and at least partly defined by said outer flexible membrane, said central cavity being open at said lower surface of said outer flexible membrane;    a first inner annular flexible membrane positioned between said base structure and said outer flexible membrane, said first inner annular flexible membrane and said base structure at least partly defining said first annular chamber;    a second inner annular flexible membrane positioned between said base structure and said outer flexible membrane, said second inner annular flexible membrane and said base structure at least partly defining said second annular chamber;    a first fluid channel connected to said first annular chamber to supply pressurized fluid to said first chamber;    a second fluid channel connected to said second annular chamber to supply pressurized fluid to said second chamber;    a third fluid channel connected to a space between said outer flexible membrane and said first and second inner annular flexible membranes, said third fluid channel being used to selectively apply suction to said space; and    a fourth fluid channel connected to said central cavity, said fourth fluid channel being used to apply suction directly to said semiconductor wafer through said central cavity to hold said semiconductor wafer onto said outer flexible membrane.    
     
     
         17 . The polishing head of  claim 16  wherein said base structure includes a base and a plurality of annular discs attached to a bottom surface of said base, said annular discs having bottom surfaces that at least partly define said first and second annular chambers.  
     
     
         18 . The polishing head of  claim 17  wherein said annular discs include a recess region on one of said bottom surfaces of said annular discs.  
     
     
         19 . The polishing head of  claim 17  wherein at least one of said annular discs has a vertical thickness that is less than the vertical thickness of other annular discs.  
     
     
         20 . A method of chucking a semiconductor wafer onto a polishing head comprising steps of: 
 positioning said semiconductor wafer against a lower surface of an outer flexible membrane of said polishing head, said outer flexible membrane being positioned below a base structure of said polishing head such that at least a first annular chamber and a second annular chamber are positioned between said base structure and said outer flexible membrane, said polishing head including a central cavity positioned below said base structure and at least partly defined by said outer flexible membrane, said central cavity being open at said lower surface of said outer flexible membrane;    reducing the pressure in said first annular chamber to deflate said first annular chamber; and    applying suction to said central cavity to chuck said semiconductor wafer onto said lower surface of said outer flexible membrane.    
     
     
         21 . The method of  claim 20  wherein said reducing said pressure in said first annular chamber includes applying suction to said first annular chamber.  
     
     
         22 . The method of  claim 20  further comprising applying a pressure to said second annular chamber such that said second annular chamber is inflated.  
     
     
         23 . The method of  claim 20  wherein said outer flexible membrane includes an annular flap on an upper surface of said outer flexible membrane, said first annular chamber being at least partly defined by said annular flap and said upper surface of said outer flexible membrane and said base structure.  
     
     
         24 . The method of  claim 23  wherein said outer flexible membrane includes another annular flap on said upper surface of said outer flexible membrane, said second annular chamber being at least partly defined by said annular flap, said another annular flap and said upper surface of said outer flexible membrane and said base structure.  
     
     
         25 . The method of  claim 24  further comprising applying a pressure to a third annular chamber such that said third annular chamber is inflated, said third annular chamber being positioned between said base structure and said outer flexible membrane, said third annular chamber being positioned to surround said second annular chamber, said third annular chamber being at least partly defined by said another annular flap and said upper surface of said outer flexible membrane and said base structure.  
     
     
         26 . The method of  claim 23  wherein said second annular chamber is at least partly defined by an inner annular flexible membrane and said base structure of said polishing head, said inner annular flexible membrane being positioned between said base structure and said outer flexible membrane.  
     
     
         27 . The method of  claim 26  further comprising applying another suction to a space between said outer flexible membrane and said inner annular flexible membrane.  
     
     
         28 . The method of  claim 26  further comprising applying a pressure to a third annular chamber such that said third annular chamber is inflated, said third annular chamber being positioned between said base structure and said outer flexible membrane, said third annular chamber being positioned to surround said second annular chamber, said third annular chamber being at least partly defined by another inner annular flexible membrane and said base structure, said another inner annular flexible membrane being positioned between said base structure and said outer flexible membrane such that said inner annular flexible membrane is surrounded by said another inner annular flexible membrane.  
     
     
         29 . The method of  claim 20  wherein said first annular chamber is at least partly defined by a first inner annular flexible membrane and said base structure, said first inner annular flexible membrane being positioned between said base structure and said outer flexible membrane, and wherein said second annular chamber is at least partly defined by a second inner annular flexible membrane, said second inner annular flexible membrane being positioned between said base structure and said outer flexible membrane.  
     
     
         30 . The method of  claim 29  further comprising applying a pressure to a third annular chamber such that said third annular chamber is inflated, said third annular chamber being positioned between said base structure and said outer flexible membrane such that said second annular chamber is surrounded by said third annular chamber, said third annular chamber being at least partly defined a third inner annular flexible membrane positioned between said base structure and said outer flexible membrane.  
     
     
         31 . The method of  claim 29  further comprising applying another suction to a space between said outer flexible membrane and said inner annular flexible membranes.