Chemical mechanical polishing edge control with pad recesses

Abstract

A Chemical Mechanical Polishing (CMP) process may generally apply more pressure around a periphery of the polishing pad than at the center of the polishing pad. This may cause uneven material removal as the substrate moves along the surface of the polishing pad. Therefore, the polishing pad may include one or more recesses around a periphery of the polishing pad to relieve pressure on the substrate. The one or more recesses may be connected to channels that extend radially outward from the recesses to the edge of the polishing pad. The recesses may collect polishing slurry during the CMP process and direct the slurry into the channels. The channels may then expel the collected polishing slurry off of the polishing pad to clear the recesses.

What is claimed is: 
     
         1 . A chemical mechanical polishing (CMP) chamber for polishing semiconductor substrates, the chamber comprising:
 a platen configured to rotate within the CMP chamber;   a polishing pad that is configured to be mounted on the platen and rotated with the platen, wherein the polishing pad comprises one or more recesses around a periphery of the polishing pad; and   a carrier head configured to hold a substrate and rotate the substrate against the polishing pad during a CMP process.   
     
     
         2 . The chamber of  claim 1 , wherein the polishing pad further comprises one or more channels around the periphery of the polishing pad that are positioned relative to the one or more recesses to direct polishing slurry out of the one or more recesses and off of the polishing pad during a CMP process. 
     
     
         3 . The chamber of  claim 2 , wherein the one or more channels comprises at least eight channels evenly spaced around the periphery of the polishing pad. 
     
     
         4 . The chamber of  claim 2 , wherein a width of the one or more recesses is tapered between the one or more channels to direct polishing slurry from the one or more recesses into the one or more channels. 
     
     
         5 . The chamber of  claim 1 , wherein the one or more recesses comprises at least one continuous circular recess having an inner radius and an outer radius around the periphery of the polishing pad. 
     
     
         6 . The chamber of  claim 1 , wherein a width of the one or more recesses is between about 4% and about 8% of a diameter of the substrate. 
     
     
         7 . A method of polishing semiconductor substrates, the method comprising:
 rotating a platen within a chemical mechanical polishing (CMP) chamber, wherein a polishing pad is mounted on the platen and rotated with the platen, and the polishing pad comprises one or more channels around a periphery of the polishing pad;   rotating a carrier head configured to hold a substrate against the polishing pad during a CMP process; and   providing a polishing slurry to the polishing pad, wherein the polishing slurry is directed off of the polishing pad through the one or more channels during the CMP process.   
     
     
         8 . The method of  claim 7 , further comprising:
 collecting the polishing slurry in a circular recess located around a periphery of the polishing pad, wherein the circular recess directs the polishing slurry into the one or more channels to be directed off of the polishing pad during the CMP process.   
     
     
         9 . The method of  claim 7 , wherein the one or more channels have a length that is directed outward perpendicular to an edge of the polishing pad and perpendicular to a circular recess around a periphery of the polishing pad. 
     
     
         10 . The method of  claim 7 , wherein the one or more channels have a length that is between about 0.5 inches and about 3.0 inches. 
     
     
         11 . The method of  claim 7 , wherein the one or more channels have a width and a depth such that a flow rate at which the polishing slurry is provided to the polishing pad is less than or equal to a flow rate at which the polishing slurry exits the polishing pad through the one or more channels. 
     
     
         12 . The method of  claim 7 , wherein the one or more channels have a width between about 0.25 inches and about 1.0 inches. 
     
     
         13 . The method of  claim 7 , wherein the one or more channels comprise at least three channels that are evenly distributed around an edge of the polishing pad. 
     
     
         14 . A polishing pad for chemical mechanical polishing (CMP) chambers, the polishing pad comprising:
 a sub pad comprising a bottom side of the polishing pad that is configured to be mounted to a platen in a CMP chamber;   a plurality of grooves on a top side of the polishing pad; and   one or more recesses around a periphery of on the top side of the polishing pad.   
     
     
         15 . The polishing pad of  claim 14 , wherein the one or more recesses comprises a circular recess having an inner radius and an outer radius to form a continuous recess within the periphery of the polishing pad. 
     
     
         16 . The polishing pad of  claim 14 , wherein the one or more recesses have a width of between about 0.2 inches and about 1.0 inches. 
     
     
         17 . The polishing pad of  claim 14 , wherein the one or more recesses are offset from an edge of the polishing pad by between about 0.5 inches and about 3.0 inches. 
     
     
         18 . The polishing pad of  claim 14 , wherein the one or more recesses have a depth that is the same as a depth of the plurality of grooves. 
     
     
         19 . The polishing pad of  claim 14 , wherein the one or more recesses have a depth that extends down to a surface of a top pad beneath the plurality of grooves and on top of the sub pad. 
     
     
         20 . The polishing pad of  claim 14 , further comprising one or more channels around the periphery of the polishing pad that are positioned relative to the one or more recesses to direct polishing slurry out of the one or more recesses and off of the polishing pad during a CMP process.