Polishing head and edge control ring thereof, and method of increasing polishing rate at wafer edge

Abstract

A polishing head used for CMP is described, including a retaining ring that is for engaging with a wafer, a membrane and an edge control ring. The membrane includes a bottom part for engaging with the wafer, and a lip part contiguous with the bottom part. The edge control ring is disposed between the retaining ring and the membrane, including a bottom part that has an abutting surface. The abutting surface of the edge control ring contacts with the external surface of the lip part of the membrane when the membrane is not inflated.

1 . A polishing head used for chemical mechanical polishing (CMP), comprising:
 a retaining ring for engaging with a wafer;   a membrane, including a bottom part and a lip part contiguous with the bottom part, wherein the bottom part is for engaging with the wafer; and   an edge control ring between the retaining ring and the membrane, which includes a bottom part having an abutting surface,   wherein the abutting surface of the edge control ring contacts with an external surface of the lip part when the membrane is not inflated.   
     
     
         2 . The polishing head of  claim 1 , wherein the abutting surface of the edge control ring and the external surface of the lip part are inclined surfaces. 
     
     
         3 . The polishing head of  claim 2 , wherein the bottom part of the edge control ring has at least one recess therein. 
     
     
         4 . The polishing head of  claim 3 , wherein the at least one recess comprises a point recess or a groove. 
     
     
         5 . The polishing head of  claim 4 , wherein the at least one recess comprises a groove and the edge control ring further comprises an O-ring in the groove. 
     
     
         6 . The polishing head of  claim 2 , wherein the edge control ring is a composite of at least two rings. 
     
     
         7 . The polishing head of  claim 6 , wherein the at least two rings comprise different materials. 
     
     
         8 . The polishing head of  claim 6 , wherein the at least two rings comprise an upper ring and a lower ring or comprise an inner ring and an outer ring. 
     
     
         9 . The polishing head of  claim 2 , wherein the edge control ring has a height adjusting mechanism thereon. 
     
     
         10 . The polishing head of  claim 2 , wherein the edge control ring is formed in an integral. 
     
     
         11 . The polishing head of  claim 2 , wherein the abutting surface of the edge control ring extends to above an edge of the lip part. 
     
     
         12 . The polishing head of  claim 1 , wherein the abutting surface of the edge control ring and the external surface of the lip part are horizontal surfaces. 
     
     
         13 . The polishing head of  claim 1 , wherein an internal surface of the lip part of the membrane is an inclined surface, and there is a gap between the internal surface of the lip part of the membrane and the bottom part of the membrane. 
     
     
         14 . The polishing head of  claim 1 , wherein the lip part is a solid part, and there is no gap between the lip part and the bottom part of the membrane. 
     
     
         15 . The polishing head of  claim 1 , wherein the lip part of the membrane comprises a material different from a material of the rest of the membrane. 
     
     
         16 . The polishing head of  claim 15 , wherein the lip part of the membrane comprises a material more rigid than a material of the rest of the membrane. 
     
     
         17 . An edge control ring that is to be mounted on a polishing head used for CMP, wherein the polishing head also comprises a membrane that has a lip part under the edge control ring and is inflated in a CMP process, the edge control ring comprising:
 an inner surface, an outer surface and a bottom part between them which has an inclined abutting surface, wherein the inclined abutting surface contacts with the lip part of the membrane when the membrane is not inflated.   
     
     
         18 . The edge control ring of  claim 17 , further comprising an extension part on the inner surface thereof to engage with the membrane. 
     
     
         19 . The edge control ring of  claim 17 , wherein the bottom part has at least one recess therein. 
     
     
         20 . The edge control ring of  claim 19 , wherein the at least one recess comprises a point recess or a groove. 
     
     
         21 . The edge control ring of  claim 20 , wherein the at least one recess comprises a point recess, further comprising an O-ring in the groove. 
     
     
         22 . The edge control ring of  claim 17 , which is a composite of at least two rings. 
     
     
         23 . The edge control ring of  claim 22 , wherein the at least two rings comprise different materials. 
     
     
         24 . The edge control ring of  claim 22 , wherein the at least two rings comprise an upper ring and a lower ring or comprise an inner ring and an outer ring. 
     
     
         25 . The edge control ring of  claim 17 , which is formed in an integral. 
     
     
         26 . The edge control ring of  claim 17 , further having a height adjusting mechanism thereon. 
     
     
         27 . A method of increasing a polishing rate at a wafer edge in a CMP process that uses a polishing head, the polishing head comprising an edge control ring and a membrane that has a lip part under the edge control ring and is inflated in the CMP process, the method comprising:
 fabricating the edge control ring and the membrane in a manner such that an abutting surface of a bottom part of the edge control ring contacts with an external surface of the lip part of the membrane when the membrane is not inflated.   
     
     
         28 . The method of  claim 27 , wherein the abutting surface of the edge control ring and the external surface of the lip part of the membrane are inclined surfaces. 
     
     
         29 . The method of  claim 27 , wherein the abutting surface of the edge control ring and the external surface of the lip part of the membrane are horizontal surfaces. 
     
     
         30 . The method of  claim 27 , wherein the abutting surface of the edge control ring extends to above an edge of the lip part of the membrane. 
     
     
         31 . The method of  claim 27 , further comprising increasing a weight of the lip part of the membrane to increase a load on the wafer edge. 
     
     
         32 . The method of  claim 31 , wherein increasing the weight of the lip part of the membrane comprises forming the lip part as a solid part. 
     
     
         33 . The method of  claim 31 , wherein increasing the weight of the lip part of the membrane comprises forming the lip part from a material that has a density higher than a density of a material of the rest of the membrane. 
     
     
         34 . The method of  claim 27 , wherein the edge control ring has a height adjusting mechanism thereon, further comprising using the height adjusting mechanism to adjust a height of the edge control ring and thereby increase a load on the wafer edge. 
     
     
         35 . The method of  claim 27 , wherein the bottom part of the edge control ring has a groove therein and the edge control ring further comprises an O-ring in the groove.