Chemical mechanical polishing method and apparatus for controlling material removal profile

Abstract

A material removal apparatus employing a showerhead with non-planar topography is provided. The showerhead surface includes a plurality of fluid zones to apply a fluid pressure to a backside of a polishing pad while a front side of the polishing-pad polishes a substrate. The varying topography of the showerhead surface and the resulting variable gap between a backside of a polishing pad and the non-planar surface of showerhead provide a well-defined fluid distribution and pressure profile for each zone. Such well-defined fluid distribution and pressure profiles, in turn, establish well-defined material removal rates on the substrate as the polishing pad polishes the substrate.

1 . An apparatus for polishing a surface of a workpiece comprising: 
 a carrier configured to hold the workpiece;    a showerhead, having a non-planar surface, providing a variable gap between the non-planar surface and the surface of the workpiece; and    a polishing pad with a polishing side and a back side positioned within the variable gap and configured to polish the surface of the workpiece with the polishing side when a fluid flow is applied from the non-planar surface to the back side.    
     
     
         2 . The apparatus of  claim 1 , wherein the fluid flow is applied from a plurality of fluid flow zones formed in the non-planar surface.  
     
     
         3 . The apparatus of  claim 1 , wherein the fluid flow zones are configured to move to cause a change in the topography of the non-planar surface.  
     
     
         4 . The apparatus of  claim 3 , wherein the fluid zones move during the polishing of the surface of the workpiece.  
     
     
         5 . The apparatus of  claim 1 , wherein the non-planar surface has a center high topography.  
     
     
         6 . The apparatus of  claim 1 , wherein the non-planar surface has a center low topography.  
     
     
         7 . The apparatus of  claim 2 , wherein at least one of the fluid flow zones is closer to the back side of the polishing pad than the rest of the fluid zones.  
     
     
         8 . The apparatus of  claim 2 , further comprising ventilation regions between the fluid flow zones.  
     
     
         9 . The apparatus of  claim 2 , wherein the fluid flow zones are concentric.  
     
     
         10 . The apparatus of  claim 2 , wherein the fluid flow zones are elongated zones.  
     
     
         11 . The apparatus of  claim 1 , wherein the fluid flow is applied from a plurality of fluid openings formed in the fluid flow zones.  
     
     
         12 . The apparatus of  claim 4 , further comprising a feed back circuit that in response to a change in a removal profile induces a change in the-topography of the non-planar surface to yield a pre-determined removal profile.  
     
     
         13 . The apparatus of  claim 2 , wherein each zone includes a variable topography.  
     
     
         14 . The apparatus of  claim 1 , wherein a polishing solution is delivered onto the polishing sid of the polishing pad during the polishing of the surface of the workpiece.  
     
     
         15 . A method of controlling material removal rate from a workpiece surface using a polishing solution, a pad and a shower head with a non-planar surface providing a variable gap between the non-planar surface and the workpiece surface, wherein the pad has a polishing side and a backside, the method comprising the steps of: 
 holding the workpiece;    placing the polishing pad into the variable gap;    emitting fluid from the non-planar surface onto the backside of the pad to establish pressure;    establishing relative motion between the pad and the workpiece surface, and    removing material from the workpiece surface with the polishing side of the pad.    
     
     
         16 . The method of  claim 15 , further comprising changing topography of the non planar surface to vary material removal profile from the surface of the workpiece.  
     
     
         17 . The method of  claim 15  wherein the step of emitting fluid comprises emitting fluid from a plurality of fluid flow zones placed in the non-planar surface.  
     
     
         18 . The method of  claim 15  further comprising the step of sensing a material removal profile during the step of removing and adjusting the variable gap to control the material removal profile.