Object holder and lithographic apparatus
An object table to support an object, the object table having a support body, an object holder to hold an object, an opening adjacent an edge of the object holder, and a channel in fluid communication with the opening via a passageway, wherein the channel is defined by a first material which is different to a second material defining the passageway.
1. An object table to support an object, the object table comprising:
a support body comprising an object holder to hold an object;
an opening adjacent an edge of the object holder; and
a channel in fluid communication with the opening via a passageway, wherein the channel is defined by a first material which is different to a second material defining the passageway; and
a thermal barrier between the first and second materials, wherein the first material forms a self-supporting structural element of the object table.
2. The object table of claim 1 , wherein the first material has a different thermal conductivity to the second material.
3. The object table of claim 2 , wherein the thermal conductivity of the first material is at least an order of magnitude larger than that of the second material.
4. The object table of claim 1 , wherein the first material has a different coefficient of thermal expansion to the second material.
5. The object table of claim 4 , wherein the coefficient of thermal expansion of the first material is at least an order of magnitude less than that of the second material.
6. The object table of claim 2 , wherein the thermal conductivity of the first material is at least an order of magnitude lower than that of the second material.
7. The object table of claim 1 , further comprising a mechanical barrier which substantially mechanically decouples the first material from the support body.
8. The object table of claim 1 , wherein the first material defines at least part of a top of the channel.
9. The object table of claim 1 , wherein the first material defines at least part of a radially inner part of the channel.
10. The object table of claim 1 , wherein the first material defines at least part of a bottom part of the channel.
11. The object table of claim 1 , wherein different properties of the first material compared to the second material result, during use, in a lower thermal load and/or a lower thermal deformation load being applied to the support body than if the first and second material were the same.
12. The object table of claim 1 , further comprising a liquid retainer in the channel to retain liquid in the channel.
13. The object table of claim 12 , wherein the liquid retainer comprises an, indentation defined on, or a projection or element present at, a bottom of the channel.
14. The object table of claim 12 , wherein the liquid retainer forms a reservoir of liquid in the channel.
15. A lithographic apparatus comprising a projection system configured to project a beam of radiation onto a radiation-sensitive substrate and an object table according to claim 1 .
16. A method of operating an immersion lithographic apparatus, comprising:
providing a liquid onto an object supported by a table; and
removing liquid from an edge of the object through an opening in fluid communication with a channel via a passageway, wherein the channel is defined by a first material which is different to a second material which defines the passageway, wherein a thermal barrier is located between the first and second materials, and wherein the first material forms a self-supporting structural element of the object table.
17. An object table to support an object, the object table comprising:
a support body comprising an object holder to hold an object;
an opening adjacent an edge of the object holder;
a channel in fluid communication with the opening via a passageway, wherein the channel is defined by a first material which is different to a second material defining the passageway; and
a mechanical barrier which substantially mechanically decouples the first material from the support body and the passageway.
18. The object table of claim 17 , comprising a thermal barrier between the first and second materials.
19. The object table of claim 17 , wherein the first material forms a self-supporting structural element of the object table.
20. The object table of claim 17 , wherein a thermal conductivity of the first material is at least an order of magnitude larger than that of the second material or a coefficient of thermal expansion of the first material is at least an order of magnitude less than that of the second material.