Baffle to reduce azimuthal etch asymmetry

Abstract

Systems and techniques for improving azimuthal symmetry in an etch process are described. In some implementations, a baffle may be used to modify the flow of gas in an etch process. A baffle may include a baffle wall, which may have at least two regions of equal radial extent. A first region may have a first open area percentage, while a fourth region may have a fourth open area percentage. The first open area percentage is smaller than the fourth open area percentage. The baffle may be positioned so that the first region is toward a vacuum inlet.

1 . A baffle comprising: 
 a baffle wall having at least some open area, the baffle wall comprising a plurality of regions each having an associated radial extent and an associated open area percentage equal to the percentage of the area of the region that is open area, the plurality of regions including a first region having a first open area percentage and a fourth region having a fourth open area percentage greater than the first open area percentage, the fourth region having an associated radial extent substantially equal to the associated radial extent of the first region; and    positioning features configured to position the baffle in an etch chamber including a vacuum inlet, the positioning features to position the first region of the baffle wall toward the vacuum inlet.    
   
   
       2 . The baffle of  claim 1 , further comprising a base flange portion.  
   
   
       3 . The baffle of  claim 2 , wherein the positioning features are included in the base flange portion.  
   
   
       4 . The baffle of  claim 1 , wherein the associated radial extent of the first region is 90 degrees.  
   
   
       5 . The baffle of  claim 1 , wherein the associated radial extent of the first region is less than 90 degrees.  
   
   
       6 . The baffle of  claim 5 , wherein the associated radial extent of the first region is equal to or greater than 30 degrees.  
   
   
       7 . The baffle of  claim 1 , wherein the plurality of regions includes a second region, the associated radial extent of the second region substantially equal to the associated radial extent of the first region and the fourth region, the second region between the first region and the second region, the second region having a second open area percentage greater than the first open area percentage.  
   
   
       8 . The baffle of  claim 7 , wherein the second open area percentage is less than the fourth open area percentage.  
   
   
       9 . A system, comprising: 
 an etch chamber;    a wafer holder positioned in the etch chamber;    a vacuum inlet in communication with the wafer holder to enable removal of gas from the etch chamber; and    a baffle including a baffle wall surrounding the wafer holder, a portion of the baffle wall positioned between the wafer holder and the vacuum inlet;    wherein the baffle wall comprises a plurality of regions, each having an associated radial extent and an associated open area percentage equal to the percentage of the area of the region that is open area, the plurality of regions including a first region having a first open area percentage and a fourth region having a fourth open area percentage greater than the first open area percentage, the fourth region having an associated radial extent substantially equal to the associated radial extent of the first region, and wherein the baffle is positioned so that the first region is positioned toward the vacuum inlet and the fourth region is positioned away from the vacuum inlet.    
   
   
       10 . The system of  claim 9 , wherein the baffle further comprises positioning features configured to position the baffle in the etch chamber, the positioning features to position the first region of the baffle wall toward the vacuum inlet.  
   
   
       11 . The system of  claim 9 , further comprising a vacuum generator in communication with the vacuum inlet.  
   
   
       12 . The system of  claim 11 , wherein the vacuum generator is a turbopump.  
   
   
       13 . The system of  claim 9 , wherein the baffle comprises a material that is not substantially degraded by an etch process associated with the etch chamber.  
   
   
       14 . The system of  claim 13 , wherein the material includes at least one of stainless steel and titanium.  
   
   
       15 . A baffle, comprising: 
 a baffle wall, the baffle wall having a top edge and a bottom edge, the baffle further having at least two regions of substantially equal radial extent, the at least two regions further extending from the top edge of the baffle to the bottom edge of the baffle, wherein the at least two regions each have an associated open area;    positioning features configured to position the baffle in an etch chamber including a vacuum inlet, the positioning features to position a first region of the at least two regions toward the vacuum inlet, wherein the first region has a minimum associated open area of the at least two regions.    
   
   
       16 . The baffle of  claim 15 , wherein the at least two regions further includes a fourth region opposite the first region, the fourth region having a maximum associated open area of the two or more regions.  
   
   
       17 . The baffle of  claim 15 , further including a second region positioned between the first region and the fourth region and having an associated open area greater than the minimum associated area and less than the maximum associated area.  
   
   
       18 . The baffle of  claim 17 , further including a third region positioned between the first region and the fourth region and having an associated open area greater than the minimum associated area and less than the maximum associated area.  
   
   
       19 . The baffle of  claim 18 , wherein the associated open area of the second region is equal to the associated open area of the third region.  
   
   
       20 . The baffle of  claim 18 , wherein the associated open area of the second region is the same as the associated open area of the third region.  
   
   
       21 . The baffle of  claim 18 , wherein the radial extent is 90 degrees.