Support table for a lithographic apparatus, lithographic apparatus and device manufacturing method
A support table for a lithographic apparatus, the support table having a support section and a conditioning system, wherein the support section, the conditioning system, or both, is configured such that heat transfer to or from a substrate supported on the support table, resulting from the operation of the conditioning system, is greater in a region of the substrate adjacent an edge of the substrate than it is in a region of the substrate that is at the center of the substrate.
1. A support table configured to support a surface of a substrate, wherein the support table comprises:
a base surface; and
a plurality of burls protruding above the base surface, each of the plurality of burls having a respective distal end, the plurality of burls arranged such that, when the substrate is supported by the support table, the substrate is supported by the respective distal end of each of the plurality of the burls,
wherein the distal ends of at least some first burls of the plurality of burls have a different surface roughness arranged to contact the substrate than the distal ends of at least some other second burls of the plurality of burls.
2. The support table of claim 1 , wherein the first burls are arranged in a region inward, relative to a center of the base surface, of a region of the second burls.
3. The support table of claim 2 , wherein the region of the second burls surrounds the region of the first burls.
4. The support table of claim 2 , wherein the first burls have a greater surface roughness than the second burls.
5. The support table of claim 1 , further comprising a plurality of protrusions, wherein the plurality of protrusions protrude above the base surface among the burls and wherein each protrusion has a height above the base surface less than the heights of the burls.
6. The support table of claim 5 , wherein the protrusions are arranged in a plurality of concentric substantially loop shapes around a central portion of the support table and each loop shape has a plurality of protrusions separated by gaps along the respective loop shape.
7. The support table of claim 6 , wherein burls are provided inward, relative to a center of the support table, of a most inward loop of protrusions and burls are provided outward, relative to the center of the support table, of a most outward loop of protrusions.
8. The support table of claim 5 , further comprising a port configured to exhaust gas, the port located between two adjacent protrusions of the plurality of protrusions.
9. The support table of claim 1 , further comprising a conditioning system configured to supply heat energy to and/or remove heat energy from the support table.
10. The support table of claim 1 , wherein a total area of burls in contact with a substrate when supported by the burls per unit area of the substrate is greater in a first region of the substrate that is adjacent an edge of the substrate than it is in a second region of the substrate that is at a central portion of the substrate.
11. A method comprising:
supporting a surface of a substrate on a support table, the support table comprising a plurality of burls protruding above a base surface of the support table, each of the plurality of burls having a respective distal end, the plurality of burls supporting the substrate by the respective distal end of each of the plurality of the burls, wherein the distal ends of at least some first burls of the plurality of burls have a different surface roughness arranged to contact the substrate than the distal ends of at least some other second burls of the plurality of burls; and
processing the substrate while supported on the support table.
12. The method of claim 11 , wherein the first burls are arranged in a region inward, relative to a center of the base surface, of a region of the second burls.
13. The method of claim 12 , wherein the region of the second burls surrounds the region of the first burls.
14. The method of claim 12 , wherein the first burls have a greater surface roughness than the second burls.
15. The method of claim 11 , wherein the processing comprises exposing the substrate with a beam of radiation.
16. A lithographic apparatus, comprising:
a support table configured to support a surface of a substrate, wherein the support table comprises:
a base surface; and
a plurality of burls protruding above the base surface, each of the plurality of burls having a respective distal end, the plurality of burls arranged such that, when the substrate is supported by the support table, the substrate is supported by the respective distal end of each of the plurality of the burls,
wherein the distal ends of at least some first burls of the plurality of burls have a different surface roughness arranged to contact the substrate than the distal ends of at least some other second burls of the plurality of burls; and
a projection system configured to project a radiation beam onto the substrate.
17. The apparatus of claim 16 , wherein the first burls are arranged in a region inward, relative to a center of the base surface, of a region of the second burls.
18. The apparatus of claim 17 , wherein the region of the second burls surrounds the region of the first burls.
19. The apparatus of claim 17 , wherein the first burls have a greater surface roughness than the second burls.
20. The apparatus of claim 16 , further comprising a liquid supply system configured to supply a liquid to a space between the projection system and the support table and the support table further comprises a conditioning system configured to supply heat energy to the support table.