Method of manufacturing a substrate support for a lithographic apparatus, substrate table, lithographic apparatus, device manufacturing method, method of use
Substrate tables and methods of manufacturing substrate supports for substrate tables. In one arrangement, a plurality of holes are formed through a base member. A burl formation member is joined to the base member. A plurality of burl structures are formed in the burl formation member. Each burl structure includes a distal surface that contacts, in use, a substrate being supported. Each burl structure has an opening to at least one of the holes formed through the base member.
1. A substrate table configured to support a substrate during a lithography process, the substrate table comprising:
a substrate support comprising:
a plurality of holes extending through a base member of the substrate support; and
a plurality of burl structures, wherein:
each burl structure comprises a distal surface configured to contact, in use, a substrate being supported by the substrate support, and each burl structure comprises openings to at least two of the holes in the base member; and
the substrate table is configured to provide an outward flow of fluid through all of the openings in each of one or more of the burl structures.
2. The substrate table of claim 1 , wherein each burl structure comprises a burl recess extending from the distal surface to a recessed surface in the burl structure, the recessed surface comprising the openings to at least two of the holes in the base member.
3. The substrate table of claim 2 , wherein the base member further comprises a plurality of base recesses in the base member, wherein each base recess is aligned with a different respective one of the burl structures on an opposite side of the base member, the alignment being such that the outward flow of fluid is provided by driving a flow of fluid through the base recess and the burl recess of the respective burl structure via the holes in the base member.
4. The substrate table of claim 3 , wherein, for each of one or more of the burl structures, when viewed perpendicularly to a plane of the base member, a cross-sectional area of each hole opening into the recessed surface in the burl recess is smaller than a cross-sectional area of the respective base recess aligned with the burl structure and smaller than a cross-sectional area of the burl recess.
5. The substrate table of claim 2 , wherein each of one or more of the burl structures comprises a wall surrounding the burl recess in directions parallel to a plane of a supported substrate in use, a distal portion of the wall forming all or a portion of the distal surface that contacts the supported substrate in use.
6. The substrate table of claim 2 , wherein each of one or more of the burl structures comprises one or more sub-burls within the burl recess of the burl structure, each sub-burl having a distal tip forming a portion of the distal surface of the burl structure that contacts, in use, the substrate supported by the substrate support, the portion being less than all of the distal surface of the burl structure.
7. The substrate table of claim 6 , wherein:
each of one or more of the burl structures comprises a wall surrounding the burl recess in directions parallel to a plane of a supported substrate in use, a distal portion of the wall forming a portion of the distal surface that contacts the supported substrate in use; and
the distal tip of each of the sub-burls is spaced apart from the distal portion of the wall in all directions parallel to the plane of the supported substrate in use.
8. The substrate table of claim 6 , wherein at least one of the holes formed through the base member passes through at least one of the sub-burls.
9. A lithographic apparatus comprising the substrate table of claim 1 , the substrate table configured to provide relative movement between a substrate and a projection system of the lithographic apparatus during exposure of the substrate in a lithography process performed by the lithographic apparatus.
10. The substrate table of claim 1 , further comprising a porous layer upstream of the openings in each of at least one of the burl structures.
11. The substrate table of claim 1 , wherein the burl structures are formed in a burl formation member joined to the base member.
12. The substrate table of claim 1 , wherein inside surfaces of the holes formed through the base member comprising a coating.
13. The substrate table of claim 1 , wherein each distal surface is in the form of a ring shape.
14. A method of manufacturing the substrate support of claim 1 , the method comprising:
forming a plurality of holes through the base member;
joining a burl formation member to the base member after the holes have been formed in the base member; and
forming the plurality of burl structures in the burl formation member, wherein the burl structures are formed such that:
each burl structure comprises a distal surface configured to contact, in use, a substrate being supported by the substrate support, and
each burl structure comprises an opening to at least one of the holes formed through the base member.
15. The method of claim 14 , wherein the plurality of burl structures are formed in the burl formation member after the burl formation member has been joined to the base member, and/or
wherein:
each burl structure comprises a burl recess extending from the distal surface to a recessed surface in the burl structure, the recessed surface comprising the opening to at least one of the holes formed through the base member; and
the recessed surface comprises a surface of the base member.
16. The method of claim 15 , wherein each burl structure comprises a burl recess extending from the distal surface to a recessed surface in the burl structure, the recessed surface comprising the opening to at least one of the holes formed through the base member.
17. The method of claim 16 , further comprising forming a plurality of base recesses in the base member, wherein each base recess is positioned so as to be aligned with a different respective one of the burl structures on an opposite side of the base member, the alignment being such that a flow of fluid can be provided in use that passes through the base recess and the burl recess of the respective burl structure via one or more of the holes formed through the base member.
18. The method of claim 17 , wherein, for each of one or more of the burl structures, when viewed perpendicularly to a plane of the base member, a cross-sectional area of each hole opening into the recessed surface in the burl recess is smaller than a cross-sectional area of the respective base recess aligned with the burl structure and smaller than a cross-sectional area of the burl recess.
19. The method of claim 16 , wherein the burl structures are formed by removing material from outside of the burl structures before removing material from inside of the burl structures to form the recessed surfaces, and/or wherein the recessed surface of each of one or more of the burl structures comprises openings to at least two of the holes formed through the base member, and/or wherein each of one or more of the burl structures comprises one or more sub-burls within the burl recess of the burl structure, each sub-burl having a distal tip forming a portion of the distal surface of the burl structure that contacts, in use, the substrate being supported by the substrate support, the portion being less than all of the distal surface of the burl structure, and/or further comprising applying a coating to the inside surfaces of the holes formed through the base member, and/or wherein the base recesses are formed before the burl structures, and/or comprising attaching the substrate support to a substrate table, the substrate table being configured to provide relative movement between the substrate and a projection system of a lithographic apparatus during exposure of the substrate in a lithography process.
20. A method of manufacturing the substrate support of claim 1 , the method comprising:
forming a plurality of holes through the base member; and
forming the plurality of burl structures in the base member after at least a portion of each of the plurality of holes has been formed in the base member, wherein the burl structures are formed such that:
each burl structure comprises a distal surface configured to contact, in use, a substrate being supported, and
each burl structure comprises an opening to at least one of the holes formed through the base member.