Polishing head for substrate polishing

Abstract

A polishing system for CMP is provided including: a polishing head assembly that includes: a shaft; and a polishing head coupled to the shaft, the polishing head including: a housing having an interior volume; a distribution plate in the interior volume of the housing; and a first conduit extending through the shaft and the interior volume of the housing to the distribution plate. The interior volume of the housing includes a first portion configured to receive a substrate below a bottom surface of the distribution plate with a back side of the substrate positioned at a first location when the substrate is retained in the polishing head, the distribution plate includes a first plurality of apertures fluidly coupled to the first conduit. A region extending from the first plurality of apertures to the first location of the back side of the substrate is free of obstructions.

What is claimed is: 
     
         1 . A polishing system for chemical mechanical planarization comprising:
 a polishing head assembly comprising:
 a shaft; and 
 a polishing head coupled to the shaft, the polishing head comprising:
 a housing having an interior volume; 
 a distribution plate in the interior volume of the housing; and 
 a first conduit extending through the shaft and the interior volume of the housing to the distribution plate, wherein 
 the interior volume of the housing includes a first portion configured to receive a substrate below a bottom surface of the distribution plate with a back side of the substrate positioned at a first location when the substrate is retained in the polishing head, 
 the distribution plate includes a first plurality of apertures fluidly coupled to the first conduit, 
 the first plurality of apertures extend through the bottom surface of the distribution plate to the first portion of the interior volume, and 
 a region extending from the first plurality of apertures to the first location of the back side of the substrate is free of obstructions. 
 
   
     
     
         2 . The polishing system of  claim 1 , further comprising a controller configured to adjust a position of one or more valves coupled to the first conduit to apply a first pressure to the first plurality of apertures during a first time period and apply a second pressure to the first plurality of apertures during a second time period. 
     
     
         3 . The polishing system of  claim 1 , further comprising a second conduit extending through the interior volume of the housing, wherein
 the distribution plate includes a second plurality of apertures fluidly coupled to the second conduit,   and the second plurality of apertures extend through the bottom surface of the distribution plate to the first portion of the interior volume.   
     
     
         4 . The polishing system of  claim 3 , wherein
 a first gas flow path is formed through the first conduit and the first plurality of apertures,   a second gas flow path is formed through the second conduit and the second plurality of apertures, and   the first gas flow path is independent of the second gas flow path.   
     
     
         5 . The polishing system of  claim 3 , further comprising a controller configured to:
 adjust a position of a first valve coupled to the first conduit to apply a first pressure to the first plurality of apertures during a first time period,   adjust a position of a second valve coupled to the second conduit to apply a second pressure to the second plurality of apertures during the first time period.   
     
     
         6 . The polishing system of  claim 5 , wherein the first pressure is a vacuum pressure and the second pressure is a pressure greater than atmospheric pressure. 
     
     
         7 . The polishing system of  claim 1 , wherein the polishing head further comprises an outer member positioned in the first portion of the interior volume of the housing, the outer member positioned below the bottom surface of the distribution plate. 
     
     
         8 . The polishing system of  claim 1 , wherein the back side of the substrate is spaced apart from the distribution plate by a gap from about 10 micron to about 200 micron when the back side of the substrate is in the first location. 
     
     
         9 . The polishing system of  claim 1 , wherein the first plurality of apertures each include one or more fins extending from a sidewall of the corresponding aperture. 
     
     
         10 . A polishing head for chemical mechanical planarization comprising:
 a housing having an interior volume;   a distribution plate in the interior volume of the housing; and   a first conduit extending through the interior volume of the housing to the distribution plate, wherein
 the interior volume of the housing includes a first portion configured to receive a substrate below a bottom surface of the distribution plate with the back side of the substrate positioned at a first location when the substrate is retained in the polishing head, 
 the distribution plate includes a first plurality of apertures fluidly coupled to the first conduit, 
 the first plurality of apertures extend through the bottom surface of the distribution plate to the first portion of the interior volume, and 
 a region extending from the first plurality of apertures to the first location of the back side of the substrate is free of obstructions. 
   
     
     
         11 . The polishing head of  claim 10 , further comprising a second conduit extending through the interior volume of the housing, wherein
 the distribution plate includes a second plurality of apertures fluidly coupled to the second conduit,   and the second plurality of apertures extend through the bottom surface of the distribution plate to the first portion of the interior volume.   
     
     
         12 . The polishing head of  claim 11 , wherein
 a first gas flow path is formed through the first conduit and the first plurality of apertures,   a second gas flow path is formed through the second conduit and the second plurality of apertures, and   the first gas flow path is independent of the second gas flow path.   
     
     
         13 . The polishing head of  claim 12 , further comprising a third conduit extending through the interior volume of the housing, wherein
 the distribution plate includes a third plurality of apertures fluidly coupled to the third conduit,   the third plurality of apertures extend through the bottom surface of the distribution plate to the first portion of the interior volume,   a third gas flow path is formed through the first conduit and the first plurality of apertures, and   the third gas flow path is independent of the first gas flow path and the second gas flow path.   
     
     
         14 . The polishing head of  claim 11 , wherein
 the bottom surface of the distribution plate has a center,   the first plurality of apertures are positioned at a first radial distance from the center of the bottom surface of the distribution plate, and   the second plurality of apertures are positioned at a second radial distance from the center of the bottom surface of the distribution plate.   
     
     
         15 . The polishing head of  claim 10 , further comprising an outer member positioned in the first portion of the interior volume of the housing, the outer member positioned below the bottom surface of the distribution plate. 
     
     
         16 . The polishing head of  claim 15 , wherein the outer member has a ring shape. 
     
     
         17 . The polishing head of  claim 15 , wherein the outer member is positioned against the bottom surface of the distribution plate. 
     
     
         18 . A method for polishing a substrate comprising:
 retaining a substrate in a polishing head in a first portion of an interior volume of the polishing head during a first time period by applying a first pressure to a first conduit coupled to a first plurality of apertures in a distribution plate of the polishing head, wherein the first plurality of apertures extend through a bottom surface of the distribution plate to the first portion of the interior volume;   positioning the substrate retained in the polishing head against a polishing pad; and   polishing the substrate by rotating a surface of the substrate against the polishing pad during a second time period occurring after the first time period while applying a second pressure to the first conduit that is coupled to the first plurality of apertures in the distribution plate, wherein the second pressure is greater than the first pressure.   
     
     
         19 . The method of  claim 18 , further comprising applying a third pressure to a second conduit coupled to a second plurality of apertures in the distribution plate of the polishing head during the second time period when the second pressure is applied to the first conduit coupled to the first plurality of apertures, wherein
 the second plurality of apertures extend through the bottom surface of the distribution plate to the first portion of the interior volume, and   the third pressure is less than the second pressure.   
     
     
         20 . The method of  claim 18 , further comprising:
 stopping the polishing of the substrate against the polishing pad during a third time period occurring after the second time period;   applying the first pressure to the first conduit coupled to the first plurality of apertures during the third time period; and   moving the polishing head with the substrate retained in the polishing head away from the polishing pad during the third time period.