Retaining ring for edge compensation by slurry flow control

Abstract

A method for chemical mechanical polishing includes bringing a substrate into contact with a polishing pad, causing relative motion between the substrate and polishing pad, dispensing a polishing liquid onto the polishing pad, holding the substrate in a lateral position with a retaining ring secured to a carrier head, and rotating the carrier head about an axis of rotation. The retaining ring has a plurality of channels extending from an inner diameter surface of the retaining ring to an outer diameter surface of the retaining ring such that rotation cause the polishing liquid to be preferentially expelled from a region below an outer edge of the substrate through the plurality of channels.

What is claimed is: 
     
         1 . A method for chemical mechanical polishing, the method comprising:
 bringing a substrate into contact with a polishing pad;   causing relative motion between the substrate and polishing pad;   dispensing a polishing liquid onto the polishing pad;   holding the substrate in a lateral position with a retaining ring secured to a carrier head, wherein the retaining ring has a plurality of channels extending from an inner diameter surface of the retaining ring to an outer diameter surface of the retaining ring; and   rotating the carrier head about an axis of rotation such that polishing liquid is preferentially expelled from a region below an outer edge of the substrate through the plurality of channels.   
     
     
         2 . The method of  claim 1 , wherein the plurality of channels are flared at the inner diameter surface of the retaining ring. 
     
     
         3 . The method of  claim 2 , wherein the plurality of channels are not flared at the outer diameter surface of the retaining ring. 
     
     
         4 . The method of  claim 1 , wherein the plurality of channels include a portion adjacent the outer diameter surface having a linear section of a leading edge of the channel and a linear section of a trailing edge of the channel. 
     
     
         5 . The method of  claim 4 , wherein the linear section of the leading edge and the linear section of the trailing are angled such that a portion of the channel therebetween narrows from inside to outside. 
     
     
         6 . The method of  claim 5 , wherein the plurality of channels are flared at the inner diameter surface of the retaining ring to widen from outside in more rapidly than the portion of the channel. 
     
     
         7 . The method of  claim 1 , wherein each respective channel of the plurality of channels is canted relative to a radial segment that extends from a center of the retaining ring to the respective channel. 
     
     
         8 . The method of  claim 7 , wherein each respective channel of the plurality of channels is canted such that the channel extends from inside out in a direction opposite to a direction of rotation of the carrier head. 
     
     
         9 . A retaining ring for a carrier head of a chemical mechanical polishing system, the retaining ring comprising:
 an annular body having an inner diameter surface, an outer diameter surface, an upper surface configured for attachment to the carrier head, and a lower surface to contact a polishing pad, wherein the lower surface has a plurality of channels extending from the inner diameter surface to the outer diameter surface, wherein the plurality of channels include a portion adjacent the outer diameter surface having a first linear section of a leading edge of the channel and a second linear section of a trailing edge of the channel that is angled relative to the first linear section such that the portion of the channel therebetween narrows from inside to outside, and wherein the plurality of channels are flared at the inner diameter surface of the retaining ring to widen from outside in more rapidly than the portion of the channel.   
     
     
         10 . The retaining ring of  claim 9 , wherein the plurality of channels are not flared at the outer diameter surface of the retaining ring. 
     
     
         11 . The retaining ring of  claim 9 , wherein the first linear portion and the second linear portion form an angle of 5-25°. 
     
     
         12 . The retaining ring of  claim 9 , wherein the plurality of channels occupy at least half of the surface area of the bottom surface. 
     
     
         13 . The retaining ring of  claim 12 , wherein the plurality of channels occupy 50-75% of the surface area of the bottom surface. 
     
     
         14 . The retaining ring of  claim 9 , wherein the plurality of channels are spaced at substantially equal intervals around a circumference of the retaining ring. 
     
     
         15 . The retaining ring of  claim 9 , wherein each respective channel of the plurality of channels is canted relative to a radial segment that extends from a center of the retaining ring to the respective channel. 
     
     
         16 . A polishing system, comprising:
 a rotatable platen to support a polishing pad;   a dispenser to deliver a polishing liquid onto the polishing pad;   a carrier head to hold a substrate against the polishing pad, the carrier head having a housing and a retaining ring secured to the housing, wherein the retaining ring has a plurality of channels extending from an inner diameter surface of the retaining ring to an outer diameter surface of the retaining ring; and   an actuator to rotate the carrier head such that the polishing liquid is preferentially expelled from a region below an outer edge of the substrate through the plurality of channels.   
     
     
         17 . The system of  claim 16 , wherein the channels are wider at the inner diameter surface than the outer diameter surface. 
     
     
         18 . The system of  claim 16 , wherein the plurality of channels include a portion adjacent the outer diameter surface having a first linear section of a leading edge of the channel and a second linear section of a trailing edge of the channel. 
     
     
         19 . The system of  claim 18 , wherein the linear section of the leading edge and the linear section of the trailing are angled such that a portion of the channel therebetween narrows from inside to outside. 
     
     
         20 . The system of  claim 19 , wherein the plurality of channels are flared at the inner diameter surface of the retaining ring to widen from outside in more rapidly than the portion of the channel.