Lithographic apparatus substrate table and method of loading a substrate

Abstract

A lithographic apparatus substrate table comprises a plurality of first projections, whereby the first projections define a first substrate supporting plane and a plurality of second projections, whereby the second projections define a second substrate supporting plane. The substrate table further comprises a clamping device configured to exert a clamping force onto the substrate. The second substrate supporting plane is parallel to the first substrate supporting plane. The second substrate supporting plane is offset in respect of the first substrate supporting plane in a direction perpendicular to the first and second substrate supporting planes. The lithographic apparatus substrate table is configured to support the substrate on the second projections at the second substrate supporting plane before application of the clamping force by the clamping device. The second projections are configured to deform upon application by the clamping device of the clamping force onto the substrate, thereby providing the substrate to move from the second substrate supporting plane to the first substrate supporting plane when clamped by the clamping device.

What is claimed is:  
     
         1 . A lithographic apparatus substrate table constructed to hold a substrate, the lithographic apparatus substrate table comprising:
 first and second projections defining corresponding a first and second substrate supporting planes plane or surface; and 
 a clamping device configured to exert a clamping force onto the substrate,second projections defining a second substrate supporting plane or surface,  
 wherein the second substrate supporting plane is parallel to the first substrate supporting plane, the second substrate supporting plane being or surface is offset with respect to the first substrate, supporting plane or surface in a direction perpendicular to the first and/or second substrate supporting planes plane or surface, 
 wherein the lithographic apparatus substrate table is configured to support the substrate on the second projections at the second substrate supporting plane or surface before application of the a clamping forceby the clamping device, and 
 wherein the second projections are configured to deform upon application by the clamping device of the clamping force onto the substrate , thereby providing the substrate to move such that a distal end of one or more of the second projections displaces from the second substrate supporting plane or surface to a location at the first substrate supporting plane when clamped by the clamping device or surface, and 
 wherein an outer periphery of each first projection is separated from and outward of an outer periphery of all of the second projections and an outer periphery of each second projection is separated from and outward of an outer periphery of all of the first projections, and 
 wherein the first and second projections comprise a same material. 
 
     
     
         2 . The lithographic apparatus substrate table of  claim 1 , wherein the substrate table comprises further comprising a plurality of burls configured for supporting the substrate, each burl being provided with having at least one first projection and at least one second projection. 
     
     
         3 . The lithographic apparatus substrate table of  claim 2 , wherein:
 a surface of at least one burl of the plurality of burl burls facing the second substrate loading supporting plane or surface has a concave shape, 
 a circumferential peripheral outer part of the at least one burl at a circumferential peripheral edge of the concave shaped surface forming forms the at least one second projection, and 
 a center part of the at least one burl forming forms the at least one first projection. 
 
     
     
         4 . The lithographic apparatus substrate table of  claim 1 , wherein the second projections comprise a spherically shaped rounded substrate carrying surface. 
     
     
         5 . The lithographic apparatus substrate table of  claim 1 , wherein the second projections comprise a flat substrate carrying surface. 
     
     
         6 . The lithographic apparatus substrate table of  claim 1 , wherein the second projections each comprise a cross section as seen extending in a direction of in the first and/or second substrate loading surfaces supporting plane or surface, which cross section increases in size towards the second substrate supporting plane or surface. 
     
     
         7 . The lithographic apparatus substrate table of  claim 1 , wherein the substrate table comprises comprising a plurality of burls configured for supporting the substrate, each of the first and second projections forming a burl. 
     
     
         8 . The lithographic apparatus substrate table of  claim 1 , wherein the amount of the first projections exceeds the amount of the second projections of the substrate table. 
     
     
         9 . The lithographic apparatus substrate table of  claim 1 , wherein a cross sectional diameter of the first projections, as seen in a direction parallel to the first and/or second substrate loading surfaces supporting plane or surface exceeds a cross sectional diameter of the first second projections. 
     
     
         10 . A lithographic apparatus comprising:
 a lithographic apparatus substrate table constructed to hold a substrate, the lithographic apparatus substrate table comprising: first and second projections defining respective first and second supporting planes, and a clamping device configured to exert a clamping force onto the substrate, wherein the second substrate supporting plane is parallel to the first substrate supporting plane, the second substrate supporting plane being offset with respect to the first substrate supporting plane in a direction perpendicular to the first and second substrate supporting planes, wherein the lithographic apparatus substrate table is configured to support the substrate on the second projections at the second substrate supporting plane before application of the clamping force by the clamping device, and wherein the second projections are configured to deform upon application by the clamping device of the clamping force onto the substrate, thereby providing the substrate to move from the second substrate supporting plane to the first substrate supporting plane when clamped by the clamping device   the substrate table of  claim 1 ;   a pattern transfer system configured to transfer a pattern onto a substrate held by the substrate table.   
     
     
         11 . A method of loading a substrate onto a substrate table of the lithographic apparatus of  claim 10 , the method comprising:
 supporting the substrate on the second projections at the second substrate supporting plane, before application of the clamping force by the clamping device; and   applying by the clamping device the clamping force onto the substrate causing the second projections to deform, thereby providing the substrate to move from the second substrate supporting plane to the first substrate supporting plane when clamped by the clamping device.   
     
     
       12. A substrate table constructed to hold a substrate, the substrate table comprising:
 first projections defining a first substrate supporting plane or surface; and   second projections defining a second substrate supporting plane or surface, the second projections interspersed among the first projections,   wherein the second substrate supporting plane or surface is offset with respect to the first substrate supporting plane or surface in a direction perpendicular to the first and/or second substrate supporting plane or surface,   wherein the substrate table is configured to support the substrate on the second projections at the second substrate supporting plane or surface before application of a clamping force,   wherein the second projections are configured to deform upon application of the clamping force onto the substrate such that the substrate displaces from the second substrate supporting plane or surface to the first substrate supporting plane or surface,   wherein an outer periphery of each first projection is separated from and outward of an outer periphery of all of the second projections and an outer periphery of each second projection is separated from and outward of an outer periphery of all of the first projections, and   wherein the second projections each comprise a cross section extending in a direction in the first and/or second substrate supporting plane or surface, which cross section increases in size towards the second substrate supporting plane or surface.   
     
     
       13. The substrate table of  claim 12 , further comprising a plurality of burls configured for supporting the substrate, each burl having at least one first projection and at least one second projection. 
     
     
       14. The substrate table of  claim 12 . comprising a plurality of burls configured for supporting the substrate, each of the first and second projections forming a burl. 
     
     
       15. The substrate table of  claim 12 , wherein the amount of the first projections exceeds the amount of the second projections of the substrate table. 
     
     
       16. The substrate table of  claim 12 , wherein a cross sectional dimension of the first projections, as seen in a direction parallel to the first and/or second substrate supporting plane or surface exceeds a cross sectional dimension of the second projections. 
     
     
       17. The substrate table of  claim 12 , wherein the second projections comprise a rounded substrate carrying surface. 
     
     
       18. A lithographic apparatus comprising:
 the substrate table of claim 12;   a pattern transfer system configured to transfer a pattern onto a substrate held by the substrate table.   
     
     
       19. The substrate table of  claim 12 , wherein a cross sectional width of each of the first projections, as seen in a direction parallel to the first and/or second substrate supporting plane or surface exceeds a cross sectional width of each of the second projections. 
     
     
       20. A substrate table constructed to hold a substrate, the substrate table comprising:
 a plurality of burls, wherein each burl comprises:
 a center part of a distal end of the burl, the center part forming a first projection, and 
 a peripheral outer part of a distal end of the burl located at a peripheral edge of the distal end of the burl so as to form a concave shape having the center part therein, the peripheral outer part forming a second projection, wherein the first projections define a first substrate supporting plane or surface, 
   wherein the second projections define a second substrate supporting plane or surface, the second substrate supporting plane or surface being offset with respect to the first substrate supporting plane or surface in a direction perpendicular to the first and/or second substrate supporting plane or surface,   wherein the substrate table is configured to support the substrate on the second projections at the second substrate supporting plane or surface before application of a clamping force, and   wherein the second projections are configured to deform upon application of the clamping force onto the substrate such that the substrate displaces from the second substrate supporting plane or surface toward the first substrate supporting plane or surface.   
     
     
       21. A lithographic apparatus comprising:
 the substrate table of claim 20;   a pattern transfer system configured to transfer a pattern onto a substrate held by the substrate table.